A children's book, but long enough to serve as a general overview on the subject for an adult who knows very little on it. The book had a chapter devoted to various "big" organizations, including the Mafia, biker gangs (in particular Hell's Angels), Yardies, the Mafiya (Russian Mafia), the Triads, and Yakuza. The history of these organizations was explained, as well as their current day practices.
An okay Further Reading list at the end of mainly adult books on these organizations specifically.