Mr. Penumbra's 24-hour bookstore

The Great Recession has shuffled Clay Jannon out of his life as a San Francisco web-design drone and landed him a new gig working the night shift at Mr. Penumbra's 24-Hour Bookstore. But after just a few days on the job, Clay begins to realize that this store is even more curious than the name suggests. There are only a few customers, but they come in repeatedly and never seem to actually buy anything. Soon he embarks on a complex analysis of the customers' behaviour and ropes his friends into helping him figure out just what's going on.