I know of two books on the Liberator, and Mike may know of other sources of information. BTW, I don't believe either book is definitive or exhaustive on the subject; such a book, AFAIK, has yet to be written.
The two books are The FP_-45 Liberator Pistol 1941-1945 by R. W. Koch, and The Liberator Pistol by Ralph Hagan. I don't know if they are still in print.
Jim