I've read Cryptonomicon at least 10 times through in the past 5 years or so.
Its fantastic. But its only about 8-900 pages, or at least my copy is (its a lot taller and wider than your average paperback, and has a gold colored cover, unlike the smaller, black colored one you find out in stores these days, which may be 1200 pages).
Baroque cycle is also fantastic (Quicksilver/ The Confusion/ The System of the World, due out soon).
I can't wait for the last installment of that.
The book is fantastic every time I go back through it, it completely rocks. I will treasure my copy until it finishes falling apart, past the point where tape can hold it together, then I will buy a new one.
Stephenson is by far my favorite living author.