Tom Vanderbilt's Traffic: Why We Drive the Way We Do (and What It Says About Us) scared me.
As you likely deduced, this book is all about traffic. It's about merging, signs, pedestrians, danger, death and scared the crap out of me. Basically, no one quite understands how to best control traffic because humans are unpredictable. Scary, yes.
Anyway, the book is well-researched, with tons of footnotes, which I appreciate. Also, his writing style is easy to follow and understand. All in all, a good nonfiction read, regardless of how it scared me. I think I'm going to work on my driving skills...