Ajax Penumbra 1969 by Robin Sloan
I bought this as a Kindle Single but I think it is available as a book as well.
This is the prequel to Mr. Penumbra's 24-Hour Bookstore. In it we meet Ajax Penumbra and learn of his upbringing and college years. We travel with Ajax to San Francisco and see how and why he stumbled into the 24-Hour Bookstore.
This was a short read but fun and entertaining and I think it is worth reading especially if you have read Mr. Penumbra's 24-Hour Bookstore.