What is the theme in Hell's Angels: A Strange and Terrible Saga by Hunter S. Thompson?

Motorcycle gangs would be the obvious theme. The text is fundamentally a book-length journalistic report about the Hell's Angels, a motorcycle outlaw gang. The overarching theme of the book is the culture and priorities of motorcycle gangs. The text seeks to answer basic questions by examining the origins of the motorcycle outlaw culture: their development over a period of perhaps twenty years; their goals, aims, and activities; and their significance in a larger social context