What is the safest way to protect the books I'm working on?

Three habits. (1) Know where your books live: each one is a plain folder under Documents\BookyAI, containing your chapters as text files plus your images and covers — any backup of that folder is a full backup of your work (Windows File History, macOS Time Machine, or copying it to a cloud-synced drive all work). (2) Keep your original manuscripts: if you imported a book from Word, keep the .docx — re-importing it recreates the book, images included. (3) Stay updated: since v1.8.2 BookyAI deletes to the Recycle Bin/Trash and automatically repairs books whose internal data file was damaged, so the two most common ways of losing work are already covered.