Without a doubt Neal Stephenson produced a masterpiece with this novel. So many interesting concepts ranging from religion, psychology, politics, technology and many more are explored and the novel is extremely well written.
Most famously, this book introduced the idea of the “metaverse” an entire world in software which rivals the real world in realism. The closest real world analogy to this we have today is Second Life. Second life lacks in realism today but there is plenty or reason to believe that we are aiming in that direction as our technology improves exponentially.
In the past few years I think voice recognition has gotten a lot better and this has sort of snuck up on us and not gotten much media attention. As we build towards a more metaverse-like technology the same thing might happen. Teleconferencing companies are GoToMeeting and toys like the Kinect pull the user into a virtual environment. They are hints at things to come.
This book also deals with what’s now called trans-humanism although the term isn’t used. The way he explores this topic is imaginative and compelling. Among the great fiction books reviewed on this site this one may be the best.