A recommendation from my lovely and literate daughter, available at the library of the University Near Here.
Mr. Penumbra's 24-Hour Bookstore is sort of a geek mystery. The protagonist, Clay Jannon, is unemployed in the Bay Area when the book opens. He was working as a web designer for the bright startup company, NewBagel, an effort by ex-Googlers who "wrote software to design and bake the platonic bagel: smooth crunchy skin, soft doughy interior, all in a perfect circle." Unfortunately, the market yawned, the ex-Googlers soon did too, and Clay started looking for work.
He happens upon the unlikely shop in the title. He is taken on as the store's second employee: Clay, Mr. Penumbra, and the other guy work 8-hour shifts, every day. The store has a smattering of normal books, but it soon becomes clear that the real purpose of the store involves the volumes on the impossibly tall shelves, a library from which a series of oddball customers return and check out volumes every so often.
Clay's curiosity gets the best of him; against the rules, he starts trying to make sense out of the special tomes. This turns out to be a life-changing quest, involving Clay's friends. (One of whom has made a small fortune with CGI software to realistically render the female bosom; he is, Clay confides, "the world's leading expert on boob physics.") We are very soon confronted with a mysterious worldwide cult/corporation, which operates in the nexus between typography, cryptography, and immortality.
The book is unusually technically accurate on some geeky details. For example, Clay is a whiz Web programmer, and his language of choice is "Ruby". Which (yes) is an actual thing commonly used for Web development.
It's a lot of fun, and (for UNHers) I've returned the library's copy, so you can snap it up.