Handle Reader Lifecycle and Errors

Task

Make the Reader safe to mount, unmount, switch books, and recover from failures.

When the component unmounts:

return () => {
  renditionRef.current?.destroy();
  bookRef.current?.destroy();
  renditionRef.current = null;
  bookRef.current = null;
};

Guard asynchronous setup so a late promise cannot update an unmounted component.

Show a Reader error state when:

• the signed URL cannot be created
• the EPUB fails to open
• the rendition cannot mount

Keep the error state inside the prepared Reader layout.

Test

Verify:

• open a valid EPUB
• switch books quickly
• leave the Reader and return
• use an invalid or missing Book ID
• simulate an EPUB load failure

No stale Reader instance should remain mounted.

Checkpoint

The Reader is a real EPUB.js integration with navigation, Contents, book-wide locations, cleanup, and error handling.

Module Complete

Readly can now open and read real EPUBs. Module 7 will persist the CFI and restore the exact reading position when the user returns.