diff --git a/backend/src/index.js b/backend/src/index.js
index 46089cb0..8c42fecd 100644
--- a/backend/src/index.js
+++ b/backend/src/index.js
@@ -180,10 +180,12 @@ app.get('/books/:book', async (req, res) => {
     }
 
     // Extract chapter numbers from filenames (e.g., "Chapter_01.md" -> "1")
-    const chapters = chapterFiles.map(file => {
+    const chapterNumbers = chapterFiles.map(file => {
       const match = file.match(/Chapter_(\d+)\.md$/);
-      return match ? parseInt(match[1], 10).toString() : null;
-    }).filter(Boolean);
+      return match ? parseInt(match[1], 10) : null;
+    }).filter(Boolean).sort((a, b) => a - b);
+
+    const chapters = chapterNumbers.map(num => num.toString());
 
     res.json({ chapters, version });
   } catch (error) {