Oh, yeah, and I'm rereading Neal Stephenson's Zodiac for the third time, and I'm noticing that it's very well written as a detective book too. That is, all the clues, even comon-knowledge clues, are presented in the text beforehand. You could theoretically figure it all out on your own. It remains engrossing, of course. There's a great scene at the beginning of chapter 20 that I need to quote for you at some point.