If you've read Freakonomics, then you already know the begining of this story.
Sudhir Venkatesh was a sociology student, when he went to the Robert Taylor Homes, in Chicago, to interview people. What he found was one of chicago's worst gang, the Black Kings, and befriended them.
In his book, "Gang Leader For a Day", Sudhir takes us back to that seven years experience, in much more detail than he did in Freakonomics.
It is a terrific read, in which we learn about the Crack trade, drive-bys, and how to reprimand an officer that's cutting the drugs before selling them.