The two books I am most familiar with are out of print, the official force history by Burhans and a smaller paperback - the author of which escapes me. My stuff is in storage for another month. If you don't already have the titles I can try and find them via an internet search and tell you a bit about the books from my recollections, if it will help.
I am sure Osprey mentions the Force in a couple of titles - it all depends on what your friend wants to know, I guess, and how much they are willing to spend.
The book SUPERCOMMANDOS is another option but I am led to believe it is mostly about uniforms and stuff and would not help your friend find out much detail on the history as, say, Burhans book. But I think it had a complete listing of Force members, as opposed to just a casualty list?