I just finished reading this a few days ago and absolutely loved it. There are references to things that mostly people in the design world will be familiar with, and as a citizen of that world, I absolutely loved it. It's really a wonderful story, even for those who have no knowledge or interest of design... that was just a fun easter egg for myself.
Without giving anything away, the story takes place in a world, not unlike our own; where the fast food empires have collapsed and the tech industry reigns during The Great Recession. The plot follows Clay Jannon as he is hired on as the night clerk at, you guessed it, Mr. Penumbra's 24-Hour Bookstore. There he encounters strange clientele who enthusiastically check-out and return huge tomes that appear to be written in code. He decides to investigate what exactly is going on at the bookstore and embarks on a journey that incorporates art, art history, design, typography, technology, archaeology, and so much more.