Stephenson writes with wonderfully dry wit and I often laugh out loud by how delightfully he's written a particular turn of phrase. The book's chapters alternate between three characters in two eras: Marine Bobby Shaftoe who discovers his aptitude for codebreaking following the attack on Pearl Harbor (he previously played glockenspiel in the band since he wouldn't be able to play the pipe organ on deck); American Lawrence Waterhouse recruited into the WWII Ultra Mega security class in Britain, where everyone on the committee seems to be a personal friend of Winston Churchill; and Randy Waterhouse, co-founder of the contemporary communications firm Epiphyte currently working in Manila.
I've likened the style to a much-more-easy-to-follow Gravity's Rainbow, perhaps mostly because of the time period, a subdued Douglas Adams and Kraken author China Mieville.
I can't imagine that I'll grow to dislike this book, though perhaps I will develop tendinitis from holding and squinting at its thick format!
12/13/2011 Have just been led to this link about an upcoming movie about Alan Turing, who is a secondary character in the book: http://www.turingfilm.com/about/overview