diff --git a/static/js/app.js b/static/js/app.js
index 1dcb443..a48d300 100644
--- a/static/js/app.js
+++ b/static/js/app.js
@@ -3099,7 +3099,7 @@ async function openBook(bookId) {
   overlay.style.display = '';
 
   try {
-    loadReaderSettings();
+    loadReaderSettings(bookId);
     const key = await getOrCreateEncKey();
     let data_ct, data_iv;
     const cached = await _getCachedBook(bookId);
@@ -3533,11 +3533,13 @@ function jumpToTocEntry(href) {
 // Reader Settings
 // ---------------------------------------------------------------------------
 
-function loadReaderSettings() {
+function loadReaderSettings(bookId) {
+  // Reset to defaults, then apply per-book overrides
+  Object.assign(readerSettings, { fontSize: 16, lineHeight: 1.8, maxWidth: 65, theme: 'dark',
+                                   pdfZoom: 100, pdfInverted: false, pdfPaginated: false, pdfSpread: false });
   try {
-    const saved = JSON.parse(localStorage.getItem('diora_reader_settings') || '{}');
+    const saved = JSON.parse(localStorage.getItem(`diora_reader_settings_${bookId}`) || '{}');
     Object.assign(readerSettings, saved);
-    // Auto-paginate on mobile if not explicitly set
     if (saved.pdfPaginated === undefined) {
       readerSettings.pdfPaginated = window.innerWidth < 768;
     }
@@ -3545,7 +3547,9 @@ function loadReaderSettings() {
 }
 
 function saveReaderSettings() {
-  localStorage.setItem('diora_reader_settings', JSON.stringify(readerSettings));
+  if (currentBookId) {
+    localStorage.setItem(`diora_reader_settings_${currentBookId}`, JSON.stringify(readerSettings));
+  }
 }
 
 function applyReaderSettings(isPdf) {