Blindsight is fantastic. The sequel, Echopraxia, is also excellent; it is very different, and I expect many people were disappointed that it wasn't just more of the same.

Also a big shout out to his less well-known novel, The Freeze Frame Revolution. It's about the crew of a "stargate"-seeding spaceship trying to stop the ship's AI, but being hampered by the fact that the AI is both near-omniscient and that they only work in short shifts before being put back in hibernation. He also wrote a handful of short stories set before and after the novel.

There's something very refreshingly direct, unvarnished, no-nonsense, and clear-eyed (some would say cynical) about Watts' style of writing. His prose tends to be tough (quite like early Gibson's noir style, with the punk attitude intact), but also beautifully cinematic. The only other write that I think comes close, aside from Gibson, is Dan Simmons with his Hyperion Cantos, but he's not nearly as darkly cynical.