diff --git a/apps/readest-app/src/__tests__/utils/library-utils.test.ts b/apps/readest-app/src/__tests__/utils/library-utils.test.ts
index 976e7796..587feba9 100644
--- a/apps/readest-app/src/__tests__/utils/library-utils.test.ts
+++ b/apps/readest-app/src/__tests__/utils/library-utils.test.ts
@@ -1184,6 +1184,47 @@ describe('secondary sort - createWithinGroupSorter (drilled-in group)', () => {
     expect(sorted.map((b) => b.metadata?.seriesIndex)).toEqual([1, 2, 3]);
   });
 
+  it('keeps each series together (in series order) when an author has multiple series', () => {
+    const books = [
+      createMockBook({
+        hash: 'b1',
+        title: 'B One',
+        metadata: { series: 'Series B', seriesIndex: 1 },
+      }),
+      createMockBook({
+        hash: 'a2',
+        title: 'A Two',
+        metadata: { series: 'Series A', seriesIndex: 2 },
+      }),
+      createMockBook({
+        hash: 'a1',
+        title: 'A One',
+        metadata: { series: 'Series A', seriesIndex: 1 },
+      }),
+      createMockBook({
+        hash: 'b2',
+        title: 'B Two',
+        metadata: { series: 'Series B', seriesIndex: 2 },
+      }),
+    ];
+    const sorter = createWithinGroupSorter(
+      LibraryGroupByType.Author,
+      LibrarySortByType.Title,
+      'en',
+      true,
+      LibrarySortByType.Series,
+    );
+    const sorted = [...books].sort(sorter);
+    // All of Series A consecutively in index order, then all of Series B —
+    // not interleaved by index across series (#1s together, #2s together).
+    expect(sorted.map((b) => `${b.metadata?.series} #${b.metadata?.seriesIndex}`)).toEqual([
+      'Series A #1',
+      'Series A #2',
+      'Series B #1',
+      'Series B #2',
+    ]);
+  });
+
   it('falls back to primary when secondary ties (same series index)', () => {
     const books = [
       createMockBook({
diff --git a/apps/readest-app/src/app/library/utils/libraryUtils.ts b/apps/readest-app/src/app/library/utils/libraryUtils.ts
index 499cce83..dee05380 100644
--- a/apps/readest-app/src/app/library/utils/libraryUtils.ts
+++ b/apps/readest-app/src/app/library/utils/libraryUtils.ts
@@ -196,8 +196,16 @@ const compareBookByKey = (a: Book, b: Book, sortBy: string, uiLanguage: string):
       return new Date(a.createdAt).getTime() - new Date(b.createdAt).getTime();
     case LibrarySortByType.Format:
       return a.format.localeCompare(b.format, uiLanguage || navigator.language);
-    case LibrarySortByType.Series:
+    case LibrarySortByType.Series: {
+      // Group by series name first so books of the same series stay consecutive,
+      // then order within a series by index. Comparing index alone would interleave
+      // series (all #1s, then all #2s) when this key is used as a secondary sort.
+      const aSeries = a.metadata?.series || '';
+      const bSeries = b.metadata?.series || '';
+      const bySeries = aSeries.localeCompare(bSeries, uiLanguage || navigator.language);
+      if (bySeries !== 0) return bySeries;
       return (a.metadata?.seriesIndex || 0) - (b.metadata?.seriesIndex || 0);
+    }
     case LibrarySortByType.Published: {
       const aPublished = a.metadata?.published || '0001-01-01';
       const bPublished = b.metadata?.published || '0001-01-01';
@@ -227,8 +235,8 @@ const compareBookByKey = (a: Book, b: Book, sortBy: string, uiLanguage: string):
 
 /**
  * @param secondarySortBy - Optional tiebreaker key applied when the primary
- *   comparison returns 0. Pass `'none'` (or omit) to disable. Series-index ties
- *   on a Series secondary fall through to the underlying primary tie.
+ *   comparison returns 0. Pass `'none'` (or omit) to disable. A Series secondary
+ *   orders by series name then index; ties on both fall through to the primary tie.
  */
 export const createBookSorter =
   (sortBy: string, uiLanguage: string, secondarySortBy: LibrarySecondarySortByType = 'none') =>