Think Like a Freak, by Steven Levitt and Stephen Dubner
These guys are like John and John of They Might be Giants. Except they have different spellings, which makes it more confusing. Anyway, I read this a while ago, procrastinated the review, and am now just going to give you a short rundown.
I guess people kept mailing the Freakonomics guys with questions about how to solve giant, intractable problems--big things like world hunger or poverty. Or about anything else anyone thought of, from breastfeeding to fracking to whether prayer works. Since they can't actually solve world hunger, they thought they'd try writing a book that explains something about how they think about problems and how economics-type thinking might be a handy tool for some of us, too. That way maybe people will stop bugging them.
It's a pretty fun book with anecdotes about soccer and lotteries, potty-training and charitable giving, and tips about how to think about problem-solving. We often try to solve problems by incentivizing some particular behavior, for example, but that can easily backfire and will always lead to some folks gaming the system for quick profit. So, they offer tips on incentive designing. Stuff like that.
I don't know that it's a world-changing book, but it was fairly entertaining. Especially the potty-training story. I don't always buy Levitt and Dubner's sometimes-facile explanations for things, but they're fun to read.