Originally Posted by Joe563
Also, if you delete/remove a book from an app/device it will be removed from the I'M READING list but will remain on the PURCHASED list. The book can then be restored by bookmarking it. It will then immediately re-appear on the I'M READING list and will re-appear on your apps/devices after the next sync.
UNLESS, you didn't purchase the book but received it as a gift... then it does not show up in 'purchased'...