A book disappeared from my Library but I never deleted it. Is my work gone?

Almost certainly not — and since v1.8.2 it comes back on its own. Every book lives as a folder on your computer (Documents\BookyAI) containing the chapters, images and covers, plus a small internal data file. If that data file gets damaged — a crash at the wrong moment, a full disk, an antivirus locking the file — older versions silently hid the book from the Library even though all the actual content was intact on disk. Since v1.8.2, BookyAI detects such a book and rebuilds the damaged file from the chapters themselves: the book reappears in your Library automatically, with its chapters, images, captions and covers — nothing to re-do. (The damaged file is kept alongside, renamed, in case support ever needs it.) If a book is missing, just update and reopen the app; if it still doesn't appear, check that the folder exists under Documents\BookyAI and contact support — do not delete anything.