That's the title of a book which I bought yesterday at Page One's Central branch.
What's it about?
Well, if you have read Freakonomics, you should remember that there is a segment in it where Steve Levitt wrote about his research on gang activities coauthored with sociologist S Venkatesh. Well, Venkatesh is the author of this new book.
Here is a short blurb of the book from Steve, here is another review by my former teacher Tyler Cowen up at Marginal Revolution.
Here is the page for the book.