In Mafia, Ed Reid gives the reader a history and overview of the organization (up to 1952, that is!). He combines his pretty thorough research primarily in narrative form which made it quite exciting. It also includes interviews, lists, an appendix, and footnotes. Although I enjoyed this colorful read, I wouldn't recommend it as a history resource as some of it is a little inaccurate.
Reid differed from his normal genre of presenting his research to mixing his research with a narrative. The result is that some of his material is inaccurate, especially his opening tale on my hometown, St. Louis. Overall, it is informative and well-researched.