Ah, I got the last book I ordered in the mail today - Tolkien and the Great War: The Threshold of Middle-earth by John Garth. Note: I'm not recommending these books I list here - aside from The Sign of the Beaver, I haven't read these books yet. The subject matter interests me, but I've heard praise and criticism on all of them. Until I read them, I reserve judgement.
That reading list is quite long, so don't expect these finished soon. But, I figure if I can find these books at a decent price, I might as well buy them.