Anyone interested in Billy the Kid and the Lincoln County War should definitely read
Frederick Nolan's "The West of Billy the Kid". It is one of the very best books on the subject!
The Authentic Life of Billy the Kid- Pat F. Garrett (1882)
The Saga of Billy the Kid- Walter Noble Burns (1926)
The Death of Billy the Kid-John W. Poe (1933)
Frontier Fighter-George W. Coe (1934)
Alias Billy the Kid- C.L. Sonnichsen and William V. Morrison (1955)
Violence In Lincoln County-William A. Keleher (1957)
The True Story of Billy the Kid: A Tale of the Lincoln County War-William Lee Hamlin (1959)
The Life and Death of John Henry Tunstall-Frederick Nolan (1965)
The Kid: Billy the Kid-Bill Rakocy (1985)
They "Knew" Billy the Kid: Interviews With Old-Time New Mexicans-Robert F. Kadlec (1987)
The Capture of Billy the Kid-James H. Earle (1988)
Billy the Kid: A Short and Violent Life-Robert M. Utley (1989)
Wilson and the Kid-Donald R. Lavash (1990)
Antrim and Billy-Don Cline (1990)
I Buried Billy-Paco Anaya (1991)
Whatever Happened To Billy the Kid?-Helen Airy (1993)
Billy the Kid: His Life and Legend-John Tuska (1994)
Billy the Kid: The Legend of El Chivato-Elizabeth Fackler (1995)
Billy the Kid: Killed in New Mexico, Died in Texas-Dr. Jannay P. Valdez and Judge Bob Hefner (1995)
Goodbye Billy the Kid-Harold L. Edwards (1995)
The Illustrated Life and Times of Billy the Kid (Second Edition)-Bob Boze Bell (1996)
Gunsmoke In Lincoln County-Philip J. Rasch (1997)
The West of Billy the Kid-Frederick Nolan (1998)
Billy the Kid: A Graphic History-Willard Ballow (1998)
Billy the Kid's Kid: The Hispanic Connection-Elbert A. Garcia (1999)
Billy the Kid: His Real Name Was....Jim Johnson (2006)
On-Line bookstores where you might find these books
Amazon Books
Alibris: A great place to find rare and out of print books
Barnes and Noble Books