New Biker Book - "Under and Alone"
A true story about a cop who goes undercover to join the Mongols was published last April, entitled "Under and Alone: The True Story of...

http://www.bikernewsonline.com/2005/06/new-biker-book-under-and-alone.htm

It sounds like an interesting read for those intrigued with biker gangs.
William Queen, who was a Vietnam Vet and an agent for the Bureau of Alcohol Tobacco & Firearms, infiltrated the Mongols as an undercover agent. According to Amazon.com:
Assuming the role of bearded biker "Billy St. John," Queen entered into a 28-month undercover operation. To gather evidence of homicide, weapons and narcotics violations, he sometimes wore a wire, knowing that its discovery could lead to his murder. Indeed, he was suspected at first of being a cop and forced to prove himself in more than a few dangerous situations. But after months of hazing, he became a trusted member.