It's A Guide To Middle Earth by Robert Foster, in the 1974 (pre-Silmarillion) paperback edition - an amazon listing of my edition. It's mostly a concordance of proper names, with some family trees in the back, apparently reprints from articles in the fanzine Niekas, but since it pre-dates *any* of the additional materials, it's mostly interesting as an item from the history of fandom, not as a reference volume.

(Or you know, just in case civilization collapses and you can't get on the internet but you really really need to know who the Heathertoes were, it might be vitally important then.)