William Monahan wrote the adapted screenplay, based on the book written by Jon Roberts (Cocaine Cowboys) and Evan Wright (Generation Kill), which recounts Jon Roberts' days as a New York drug smuggler and gun runner. Here's an official description of the book.
"In 2008 veteran journalist Evan Wright, acclaimed for his New York Times bestselling book Generation Kill and co-writer of the Emmy-winning HBO series it spawned, began a series of conversations with super-criminal Jon Roberts, star of the fabulously successful documentary Cocaine Cowboys. Those conversations would last three years, during which time Wright came to realize that Roberts was much more than the de-facto "transportation chief" of the Medellin Cartel during the 1980s, much more than a facilitator of a national drug epidemic. As Wright's tape recorder whirred and Roberts unburdened himself of hundreds of jaw-dropping tales, it became clear that perhaps no one in history had broken so many laws with such willful abandon.
Roberts, in fact, seemed to be a prodigy of criminality - but one with a remarkable self-awareness and a fierce desire to protect his son from following the same path.
American Desperado is Roberts' no-holds-barred account of being born into Mafia royalty, witnessing his first murder at the age of seven, becoming a hunter-assassin in Vietnam, returning to New York to become -- at age 22 -- one of the city's leading nightclub impresarios, then journeying to Miami where in a few short years he would rise to become the Medellin Cartel's most effective smuggler."