diff --git a/booklore-api/src/main/java/com/adityachandel/booklore/mobile/dto/MobileBookDetail.java b/booklore-api/src/main/java/com/adityachandel/booklore/mobile/dto/MobileBookDetail.java
new file mode 100644
index 000000000..b60400ec0
--- /dev/null
+++ b/booklore-api/src/main/java/com/adityachandel/booklore/mobile/dto/MobileBookDetail.java
@@ -0,0 +1,80 @@
+package com.adityachandel.booklore.mobile.dto;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import lombok.Builder;
+import lombok.Data;
+
+import java.time.Instant;
+import java.time.LocalDate;
+import java.util.List;
+import java.util.Set;
+
+/**
+ * Full DTO for book detail view on mobile.
+ * Contains all fields needed for the book detail screen.
+ */
+@Data
+@Builder
+@JsonInclude(JsonInclude.Include.NON_NULL)
+public class MobileBookDetail {
+    // Basic fields (same as MobileBookSummary)
+    private Long id;
+    private String title;
+    private List<String> authors;
+    private String thumbnailUrl;
+    private String readStatus;
+    private Integer personalRating;
+    private String seriesName;
+    private Float seriesNumber;
+    private Long libraryId;
+    private Instant addedOn;
+    private Instant lastReadTime;
+
+    // Additional detail fields
+    private String subtitle;
+    private String description;
+    private Set<String> categories;
+    private String publisher;
+    private LocalDate publishedDate;
+    private Integer pageCount;
+    private String isbn13;
+    private String language;
+    private Double goodreadsRating;
+    private Integer goodreadsReviewCount;
+    private String libraryName;
+    private List<MobileShelfSummary> shelves;
+    private Float readProgress;
+    private String primaryFileType;
+    private List<String> fileTypes;
+    private List<MobileBookFile> files;
+
+    // Reading position progress for resume
+    private EpubProgress epubProgress;
+    private PdfProgress pdfProgress;
+    private CbxProgress cbxProgress;
+
+    @Data
+    @Builder
+    public static class EpubProgress {
+        private String cfi;
+        private String href;
+        private Float percentage;
+        private Instant updatedAt;
+    }
+
+    @Data
+    @Builder
+    public static class PdfProgress {
+        private Integer page;
+        private Float percentage;
+        private Instant updatedAt;
+    }
+
+    @Data
+    @Builder
+    public static class CbxProgress {
+        private Integer page;
+        private Float percentage;
+        private Instant updatedAt;
+    }
+}
diff --git a/booklore-api/src/main/java/com/adityachandel/booklore/mobile/mapper/MobileBookMapper.java b/booklore-api/src/main/java/com/adityachandel/booklore/mobile/mapper/MobileBookMapper.java
new file mode 100644
index 000000000..29d2b7df8
--- /dev/null
+++ b/booklore-api/src/main/java/com/adityachandel/booklore/mobile/mapper/MobileBookMapper.java
@@ -0,0 +1,249 @@
+package com.adityachandel.booklore.mobile.mapper;
+
+import com.adityachandel.booklore.mobile.dto.MobileBookDetail;
+import com.adityachandel.booklore.mobile.dto.MobileBookFile;
+import com.adityachandel.booklore.mobile.dto.MobileBookSummary;
+import com.adityachandel.booklore.mobile.dto.MobileLibrarySummary;
+import com.adityachandel.booklore.mobile.dto.MobileMagicShelfSummary;
+import com.adityachandel.booklore.mobile.dto.MobileShelfSummary;
+import com.adityachandel.booklore.model.entity.*;
+import org.mapstruct.*;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+@Mapper(componentModel = "spring", unmappedTargetPolicy = ReportingPolicy.IGNORE)
+public interface MobileBookMapper {
+
+    @Mapping(target = "id", source = "book.id")
+    @Mapping(target = "title", source = "book.metadata.title")
+    @Mapping(target = "authors", source = "book.metadata.authors", qualifiedByName = "mapAuthors")
+    @Mapping(target = "thumbnailUrl", source = "book", qualifiedByName = "mapThumbnailUrl")
+    @Mapping(target = "readStatus", source = "progress.readStatus")
+    @Mapping(target = "personalRating", source = "progress.personalRating")
+    @Mapping(target = "seriesName", source = "book.metadata.seriesName")
+    @Mapping(target = "seriesNumber", source = "book.metadata.seriesNumber")
+    @Mapping(target = "libraryId", source = "book.library.id")
+    @Mapping(target = "addedOn", source = "book.addedOn")
+    @Mapping(target = "lastReadTime", source = "progress.lastReadTime")
+    MobileBookSummary toSummary(BookEntity book, UserBookProgressEntity progress);
+
+    @Mapping(target = "id", source = "book.id")
+    @Mapping(target = "title", source = "book.metadata.title")
+    @Mapping(target = "authors", source = "book.metadata.authors", qualifiedByName = "mapAuthors")
+    @Mapping(target = "thumbnailUrl", source = "book", qualifiedByName = "mapThumbnailUrl")
+    @Mapping(target = "readStatus", source = "progress.readStatus")
+    @Mapping(target = "personalRating", source = "progress.personalRating")
+    @Mapping(target = "seriesName", source = "book.metadata.seriesName")
+    @Mapping(target = "seriesNumber", source = "book.metadata.seriesNumber")
+    @Mapping(target = "libraryId", source = "book.library.id")
+    @Mapping(target = "addedOn", source = "book.addedOn")
+    @Mapping(target = "lastReadTime", source = "progress.lastReadTime")
+    @Mapping(target = "subtitle", source = "book.metadata.subtitle")
+    @Mapping(target = "description", source = "book.metadata.description")
+    @Mapping(target = "categories", source = "book.metadata.categories", qualifiedByName = "mapCategories")
+    @Mapping(target = "publisher", source = "book.metadata.publisher")
+    @Mapping(target = "publishedDate", source = "book.metadata.publishedDate")
+    @Mapping(target = "pageCount", source = "book.metadata.pageCount")
+    @Mapping(target = "isbn13", source = "book.metadata.isbn13")
+    @Mapping(target = "language", source = "book.metadata.language")
+    @Mapping(target = "goodreadsRating", source = "book.metadata.goodreadsRating")
+    @Mapping(target = "goodreadsReviewCount", source = "book.metadata.goodreadsReviewCount")
+    @Mapping(target = "libraryName", source = "book.library.name")
+    @Mapping(target = "shelves", source = "book.shelves", qualifiedByName = "mapShelves")
+    @Mapping(target = "readProgress", source = "progress", qualifiedByName = "mapReadProgress")
+    @Mapping(target = "primaryFileType", source = "book", qualifiedByName = "mapPrimaryFileType")
+    @Mapping(target = "fileTypes", source = "book", qualifiedByName = "mapFileTypes")
+    @Mapping(target = "files", source = "book", qualifiedByName = "mapFiles")
+    @Mapping(target = "epubProgress", source = "progress", qualifiedByName = "mapEpubProgress")
+    @Mapping(target = "pdfProgress", source = "progress", qualifiedByName = "mapPdfProgress")
+    @Mapping(target = "cbxProgress", source = "progress", qualifiedByName = "mapCbxProgress")
+    MobileBookDetail toDetail(BookEntity book, UserBookProgressEntity progress);
+
+    @Named("mapAuthors")
+    default List<String> mapAuthors(Set<AuthorEntity> authors) {
+        if (authors == null || authors.isEmpty()) {
+            return Collections.emptyList();
+        }
+        return authors.stream()
+                .map(AuthorEntity::getName)
+                .collect(Collectors.toList());
+    }
+
+    @Named("mapCategories")
+    default Set<String> mapCategories(Set<CategoryEntity> categories) {
+        if (categories == null || categories.isEmpty()) {
+            return Collections.emptySet();
+        }
+        return categories.stream()
+                .map(CategoryEntity::getName)
+                .collect(Collectors.toSet());
+    }
+
+    @Named("mapThumbnailUrl")
+    default String mapThumbnailUrl(BookEntity book) {
+        if (book == null || book.getId() == null) {
+            return null;
+        }
+        return "/api/books/" + book.getId() + "/cover";
+    }
+
+    @Named("mapShelves")
+    default List<MobileShelfSummary> mapShelves(Set<ShelfEntity> shelves) {
+        if (shelves == null || shelves.isEmpty()) {
+            return Collections.emptyList();
+        }
+        return shelves.stream()
+                .map(this::toShelfSummary)
+                .collect(Collectors.toList());
+    }
+
+    default MobileShelfSummary toShelfSummary(ShelfEntity shelf) {
+        if (shelf == null) {
+            return null;
+        }
+        return MobileShelfSummary.builder()
+                .id(shelf.getId())
+                .name(shelf.getName())
+                .icon(shelf.getIcon())
+                .bookCount(shelf.getBookEntities() != null ? shelf.getBookEntities().size() : 0)
+                .publicShelf(shelf.isPublic())
+                .build();
+    }
+
+    @Named("mapReadProgress")
+    default Float mapReadProgress(UserBookProgressEntity progress) {
+        if (progress == null) {
+            return null;
+        }
+        // Try KoReader progress first, then Kobo progress
+        if (progress.getKoreaderProgressPercent() != null) {
+            return progress.getKoreaderProgressPercent();
+        }
+        if (progress.getKoboProgressPercent() != null) {
+            return progress.getKoboProgressPercent();
+        }
+        return null;
+    }
+
+    @Named("mapEpubProgress")
+    default MobileBookDetail.EpubProgress mapEpubProgress(UserBookProgressEntity progress) {
+        if (progress == null || progress.getEpubProgress() == null) {
+            return null;
+        }
+        return MobileBookDetail.EpubProgress.builder()
+                .cfi(progress.getEpubProgress())
+                .href(progress.getEpubProgressHref())
+                .percentage(progress.getEpubProgressPercent())
+                .updatedAt(progress.getLastReadTime())
+                .build();
+    }
+
+    @Named("mapPdfProgress")
+    default MobileBookDetail.PdfProgress mapPdfProgress(UserBookProgressEntity progress) {
+        if (progress == null || progress.getPdfProgress() == null) {
+            return null;
+        }
+        return MobileBookDetail.PdfProgress.builder()
+                .page(progress.getPdfProgress())
+                .percentage(progress.getPdfProgressPercent())
+                .updatedAt(progress.getLastReadTime())
+                .build();
+    }
+
+    @Named("mapCbxProgress")
+    default MobileBookDetail.CbxProgress mapCbxProgress(UserBookProgressEntity progress) {
+        if (progress == null || progress.getCbxProgress() == null) {
+            return null;
+        }
+        return MobileBookDetail.CbxProgress.builder()
+                .page(progress.getCbxProgress())
+                .percentage(progress.getCbxProgressPercent())
+                .updatedAt(progress.getLastReadTime())
+                .build();
+    }
+
+    @Named("mapPrimaryFileType")
+    default String mapPrimaryFileType(BookEntity book) {
+        if (book == null) {
+            return null;
+        }
+        BookFileEntity primaryFile = book.getPrimaryBookFile();
+        if (primaryFile != null && primaryFile.getBookType() != null) {
+            return primaryFile.getBookType().name();
+        }
+        return null;
+    }
+
+    @Named("mapFileTypes")
+    default List<String> mapFileTypes(BookEntity book) {
+        if (book == null || book.getBookFiles() == null || book.getBookFiles().isEmpty()) {
+            return Collections.emptyList();
+        }
+        return book.getBookFiles().stream()
+                .filter(bf -> bf.getBookType() != null)
+                .map(bf -> bf.getBookType().name())
+                .distinct()
+                .collect(Collectors.toList());
+    }
+
+    @Named("mapFiles")
+    default List<MobileBookFile> mapFiles(BookEntity book) {
+        if (book == null || book.getBookFiles() == null || book.getBookFiles().isEmpty()) {
+            return Collections.emptyList();
+        }
+        BookFileEntity primaryFile = book.getPrimaryBookFile();
+        Long primaryId = primaryFile != null ? primaryFile.getId() : null;
+
+        return book.getBookFiles().stream()
+                .filter(bf -> bf.getBookType() != null && bf.isBook())
+                .map(bf -> MobileBookFile.builder()
+                        .id(bf.getId())
+                        .bookType(bf.getBookType().name())
+                        .fileSizeKb(bf.getFileSizeKb())
+                        .fileName(bf.getFileName())
+                        .isPrimary(bf.getId().equals(primaryId))
+                        .build())
+                .collect(Collectors.toList());
+    }
+
+    default MobileLibrarySummary toLibrarySummary(LibraryEntity library, long bookCount) {
+        if (library == null) {
+            return null;
+        }
+        return MobileLibrarySummary.builder()
+                .id(library.getId())
+                .name(library.getName())
+                .icon(library.getIcon())
+                .bookCount(bookCount)
+                .build();
+    }
+
+    default MobileShelfSummary toShelfSummaryFromEntity(ShelfEntity shelf) {
+        if (shelf == null) {
+            return null;
+        }
+        return MobileShelfSummary.builder()
+                .id(shelf.getId())
+                .name(shelf.getName())
+                .icon(shelf.getIcon())
+                .bookCount(shelf.getBookEntities() != null ? shelf.getBookEntities().size() : 0)
+                .publicShelf(shelf.isPublic())
+                .build();
+    }
+
+    default MobileMagicShelfSummary toMagicShelfSummary(MagicShelfEntity magicShelf) {
+        if (magicShelf == null) {
+            return null;
+        }
+        return MobileMagicShelfSummary.builder()
+                .id(magicShelf.getId())
+                .name(magicShelf.getName())
+                .icon(magicShelf.getIcon())
+                .iconType(magicShelf.getIconType() != null ? magicShelf.getIconType().name() : null)
+                .publicShelf(magicShelf.isPublic())
+                .build();
+    }
+}