Someone earlier asked for a title of a book that would help them appreciate Fuller's films more, and I cannot recommend enough his autobiography. Before reading it my interest in Fuller was tepid at best. I didn't consider him to be in the upper "ranks" of American filmmakers, despite enjoying Shock Corridor a lot and mildly enjoying Naked Kiss and Pickup on South Street. After reading his book though I was not only thoroughly entertained by the countless anecdotes about the filmmaking industry and WWII but I was just blown away by the passion and sincerity by Mr. Fuller. Upon rewatching his films after reading the book I gained a new found respect and enjoyment out of them. I now consider him one of the true maverick filmmakers period. Sure he might not be the most technically sound or have the most breathtaking mis-en-scene or montages, but his films just have this raw, real quality to them that sets him apart from some of the more "artistic" filmmakers.
Just to add to BrightEyes23's post, Sam Fuller's autobiography is called A Third Face: My Tale of Writing, Fighting and Filmmaking
Coincidentally, I was at a friend's house yesterday, and noticed this on his bookshelf. While my friend took a phone call, I opened the book and began reading, and wound up borrowing the book. It's excellent! Scorsese's intro is good, and Fuller's writing style is incredibly engaging. I was hooked on the first page.