Solid science fiction from Neil Stephenson. It's hard to describe the plot of this book, I'm not even sure there is one in the conventional sense. The book tracks many characters across different timelines and has no problem jumping from one event that seems like it might be the main plot line to a completely different one. Everything is connected but the whole that it forms doesn't have a clear structure.
Worth reading for Stephenson's style, which is always great, the cryptography explanations, and a description of digital gold before bitcoin (apparently this was required reading at Paypal in the early days).