These first two are a must have for anyone interested in studying The Kid. Frederick Nolan is the preeminent historian when it comes to not only Billy but the entire Lincoln County War. I advise you to start there. At the bottom of this page is some Historical Fiction about The Kid.
The Lincoln County War: A Documentary History
The West of Billy the Kid
The Authentic Life of Billy the Kid
To Hell on a Fast Horse
Billy the Kid: The Endless Ride
This book by Roy Haws does a pretty good job taking care of this Brushy Bill nonsense. Even better is that Mr. Haws is a relative of Brushy Bill who has plenty of documentation. Roberts’ being The Kid should have been put to bed long ago. Unfortunately with the release of Young Guns II in 1990, and believing they were apparently watching a documentary, it made everyone an expert on the subject. Robert Stack didn’t help matters with his Unsolved Mysteries episode. Brad Meltzer brought it up again in 2011, and even more frustrating was the travesty by Bill O’Reilly known as Legends and Lies: The Real West. A book and documentary filled with inaccuracies, speculation, and rumor. Something that should not be contained in a show entitled such as it was.
Here is a link for a free online version of his book. Please remember he took a lot of time writing it so it would be appreciated if you would eventually buy a copy. You don’t even have to use my affiliate link to do so. Just so long as you buy it somewhere to at least pay him for is wonderful work.
Bandita Bonita: Romancing Billy the Kid, A Novel