This was an interesting read. At a bit over 900 pages in an oversize paperback edition, it was a huge, long read as well. That's part of why you haven't heard much from me lately. Well, that and work.
I enjoyed this book a fair bit, actually. The first third or so might have been a bit slow - it took me a long time to get through it - but the rest went reasonably quickly. This is a geek book, though. It discusses any number of topics in depth, possibly far more depth than you're interested in reading if you're not a geek. Happily I am a geek and it worked well for me.
The plot revolves around the interconnected lives of several people at two different times: during the second world war and now. In particular we follow a marine in WW II, and cryptographer and mathematician working in WW II, and a programmer working now. Others factor in, of course, but those are the three main points of view. The marine winds up doing and seeing all kinds of interesting things during the war, some of which are never adequately explained, the cryptographer is more straight forward in some ways, and the programmer could be any of a number of people I know, at least in terms of background.
I think that - apart from it's sheer size - Cryptonomicon is an approachable book by Stephenson. I've read two others by him Snow Crash and The Diamond Age. For my money, this may be the best of the three. If you're looking for something substantial to read, this might be it. I ought to get credit for 3 or 4 regular books on page count alone.