This is an action adventure with zeppelins and dragons and detectives and fae. Irene is a Librarian, bound to serve the Invisible Library which sits between alternate worlds. Her job usually entails entering an alternate under cover, picking up a particularly unusual book, and returning to base. This time she's sent to an alternative London which has a high chaos infestation, making it a more dangerous assignment -- and she's asked to take a trainee along for the ride. This London has a steampunk feel, and it's not long before she runs into Vale, a great detective in the Sherlock Holmes tradition (with a number of in-jokes for Holmes fans). Between them, they must find the missing book before anyone more dangerous gets their hands on it. Every bit as fun and silly as it sounds.