Many years ago, Claire was named Head Librarian of the Unwritten Wing-- a neutral space in Hell where all the stories unfinished by their authors reside. Her job consists mainly of repairing and organizing books, but also of keeping an eye on restless stories that risk materializing as characters and escaping the library. When a Hero escapes from his book and goes in search of his author, Claire must track and capture him with the help of former muse and current assistant Brevity and nervous demon courier Leto.

But what should have been a simple retrieval goes horrifyingly wrong when the terrifyingly angelic Ramiel attacks them, convinced that they hold the Devil's Bible. The text of the Devil's Bible is a powerful weapon in the power struggle between Heaven and Hell, so it falls to the librarians to find a book with the power to reshape the boundaries between Heaven, Hell....and Earth.