I read quite a few others that have been mentioned here, but I finally read two that hard sci-fi books that should appeal to the Hacker News crowd

Permutation City: People can run simulations of themselves or entirely migrate their consciousness into computer programs, but existence is often limited to the amount of computation that you can afford, leading to slow existences that stretch time into fractions of realtime. That premise had me hooked, but the book has fantastic thought provoking plot points throughout. Highly recommended. http://www.amazon.com/Permutation-City-Novel-Greg-Egan/dp/15...

Blindsight: Amazing first alien encounter book that should be read by everyone that is a fan of the genre. Memorable cast of characters...the Vampires are really interesting. All kinds of introductory scientific concepts throughout. Entertaining and educational. http://www.amazon.com/Blindsight-Peter-Watts/dp/0765319640/r...