Everything and More: A Compact History of ∞
Looking forward to this, had no idea it existed until recently. Plus, I'm a big fan of DFW's nonfiction.
Follow-up: Wow, what a tough read. My math education ended with trig in high school, aside from a required statistics course for my psychology major, so 90% went over my head. This book was actually easier to understand from a philosophy major viewpoint.