The Mara Salvatrucha, or MS-13, is a fairly notorious gang. I like reading about gangs in general, and in particular this book was well-written, a real page-turner.
I’m not going to reveal a lot of the details, because you should just read the book. It largely covers the life and case of one informant, Brenda Paz, weaving in a background of the gang and its history, customs, processes, norms, etc.
Really, really good book.