Freakonomics subtitle is: "A Rogue Economist Explores the Hidden Side of Everything". The authors, Steven Levitt, a University of Chicago Economics professor, and Stephen Dubner, a journalist, proclaim that there is no uniting theme to the book. Generally the book is about using the tools of economics to look at some odd and sometimes interesting questions.
"What do schoolteachers and Sumo Wrestlers have in common?" and "How is the Ku Klux Klan like a Group of Real Estate Agents?" I started reading the book expecting that it would challenge conventional wisdom on a number of topics. However, the best contribution this book makes is that it challenges (at least my) conventional paradigms on how to look at and answer any particular question.
At times their arguments were convincing and surprising. But in general, I found either their reasoning incomplete or possibly irrelevant (the parenting sections) or their positions unsurprising (on Real Estate Agents).
Still, it is a worthwhile read. And the authors have a blog (here).