Clay Jannon needs a job. He lost his job in the the great food-chain contraction of the early twenty-first century. When he sees a “Help Wanted” sign in the window of Mr. Penumbra’s 24-Hour Bookstore, he inquires inside and is hired on the spot. The front of the store is a haphazard collection of the types of books one finds in a normal used book store. But the back of the store, well, the back of the store contains the tomes that Clay has dubbed the Waybacklist. As far as Clay can tell, these books don’t exist anywhere else in the world other than in Mr. Penumbra’s store. They are filled with code, and they’re not for sale. The Waybacklist books are borrowed by a select group of odd personages who come into the store, return the last volume they borrowed and then move onto the next. When Clay starts to figure out that there’s a pattern to the volumes they borrow, he and his (rather eccentric) group of friends start using a computer model of the store and the volumes borrowed to decipher the pattern. Things only get stranger from there.

Mr. Penumbra’s 24-Hour Bookstore is a story of knowledge lost, the search for the answer to eternal life, the tension between old technology and new, and the things a person can accomplish when one is willing to learn and try new things.