The Sleepwalkers

This one started slowly for me, and I wasn't sold on it at all, especially as the initial viewpoint character is not at all sympathetic. And then suddenly I found myself at 40% and racing through the pages and reassessing my opinion of, well, everybody in the story. It's very cleverly structured, and I think a reread armed with the knowledge of what happens would be very productive. Not necessarily an easy read, but a very good one.