diff --git a/src/components/EditorView.tsx b/src/components/EditorView.tsx
index e98d81b..ec03970 100644
--- a/src/components/EditorView.tsx
+++ b/src/components/EditorView.tsx
@@ -274,6 +274,9 @@ export function EditorView() {
                   content={chapter.content}
                   onChange={(content) => setChapterContent(chapter.id, content)}
                   onReady={setEditor}
+                  onContentError={() =>
+                    setNotice("This chapter contains content Margin couldn't fully read; editing may drop the unrecognized parts.")
+                  }
                 />
               </article>
               <FloatingToolbar editor={editor} />
diff --git a/src/editor/Editor.tsx b/src/editor/Editor.tsx
index 972f96f..0a03738 100644
--- a/src/editor/Editor.tsx
+++ b/src/editor/Editor.tsx
@@ -10,11 +10,14 @@ interface EditorProps {
   content: JSONContent;
   onChange: (content: JSONContent) => void;
   onReady: (editor: TiptapEditor | null) => void;
+  onContentError: (error: Error) => void;
 }
 
-export function Editor({ bookId, chapterId, content, onChange, onReady }: EditorProps) {
+export function Editor({ bookId, chapterId, content, onChange, onReady, onContentError }: EditorProps) {
   const onChangeRef = useRef(onChange);
   onChangeRef.current = onChange;
+  const onContentErrorRef = useRef(onContentError);
+  onContentErrorRef.current = onContentError;
 
   const latest = useRef<ChapterPosition | null>(null);
 
@@ -22,7 +25,9 @@ export function Editor({ bookId, chapterId, content, onChange, onReady }: Editor
     extensions: editorExtensions,
     content,
     immediatelyRender: false,
+    enableContentCheck: true,
     editorProps: { attributes: { class: "prose" } },
+    onContentError: ({ error }) => onContentErrorRef.current(error),
     onUpdate: ({ editor }) => onChangeRef.current(editor.getJSON()),
   });
 
diff --git a/src/library.ts b/src/library.ts
index cdd84ef..e3a145e 100644
--- a/src/library.ts
+++ b/src/library.ts
@@ -1,6 +1,6 @@
 import { invoke } from "@tauri-apps/api/core";
 import { isDesktop } from "./ipc";
-import { type Book, createBook, starterBook } from "./model/book";
+import { type Book, SCHEMA_VERSION, createBook, schemaVersion, starterBook } from "./model/book";
 
 export interface BookSummary {
   id: string;
@@ -16,11 +16,16 @@ export async function listBooks(): Promise<BookSummary[]> {
 
 export async function loadBook(id: string): Promise<Book> {
   const contents = await invoke<string>("load_book", { id });
+  let book: Book;
   try {
-    return JSON.parse(contents) as Book;
+    book = JSON.parse(contents) as Book;
   } catch {
     throw new Error("the book file is corrupt or unreadable");
   }
+  if (schemaVersion(book.schema) > SCHEMA_VERSION) {
+    throw new Error("this book was made with a newer version of Margin; update the app to open it");
+  }
+  return book;
 }
 
 export async function saveBook(book: Book): Promise<void> {
diff --git a/src/model/book.ts b/src/model/book.ts
index dc8017e..4e78be3 100644
--- a/src/model/book.ts
+++ b/src/model/book.ts
@@ -115,6 +115,14 @@ export interface Book {
   chapters: Chapter[];
 }
 
+export const SCHEMA_VERSION = 1;
+
+export function schemaVersion(schema: unknown): number {
+  if (typeof schema !== "string") return 0;
+  const match = /^margin\/(\d+)$/.exec(schema);
+  return match ? Number(match[1]) : 0;
+}
+
 function paragraph(text: string): JSONContent {
   return { type: "paragraph", content: [{ type: "text", text }] };
 }