«Ajax Penumbra» by Robin Sloan

The utterly charming prequel to the New York Times-bestseller Mr Penumbra's 24-hour Bookstore.
San Francisco, 1969. The summer of drugs, music and a new age dawning. A young, earnest Ajax Penumbra has been given his first assignment as a Junior Acquisitions Officer — to find the single surviving copy of the Techne Tycheon, a mysterious volume that has brought and lost great fortune for anyone who has owned it. After a few weeks of rigorous hunting, Penumbra feels no closer to his goal than when he started. But late one night, after another day of dispiriting dead ends, he stumbles upon a 24-hour bookstore and the possibilities before him expand exponentially. With the help of his friend's homemade computer, an ancient map, a sunken ship and the vast shelves of the 24-hour bookstore, Ajax Penumbra might just find what he's seeking…