Can anyone else access my book?

No. Your book is stored in your browser on your computer. Other users can't reach it, and there's no public link to it.

If you've backed a book up to your account, or you have a Concierge delivery, that copy is tied to your account and is only served to a signed-in session on that account. It isn't listed anywhere, it isn't shared, and it isn't indexed. See Do you store my manuscript or cover files?

The situation worth thinking about

A shared or public computer. Since the book lives in that browser, the next person could open My Books and see it. If you ever work on a computer that isn't yours:

• Use the "Erase everything on this device" button on the My Books page when you're done. It signs you out and wipes every local project. See How can I permanently delete a local project?
• Or do your work in a private/incognito window, which discards everything on close (just remember to download your project file first, or you'll lose it too).

Signing out on a shared computer matters more if you've used cloud backup, because a signed-in session is what reaches those copies.