I don't know if there were any new editions. I presume there must be. I'll look that one up. I know davem has a nice hardback copy with colour plate illustrations by Ted Nasmith but I've never checked if it's updated text to be honest! Why? I tend to use my ancient paperback copy - might well be the same one you used, Bricho; it used to 'live' next to the novels as it was so invaluable for reference.
Illustrated version and
non-illustrated version .
The Lord of the Rings, a Reader's Companion closely mirrors the text of Lord of the Rings and is superb for a close read-through, fully recommended. And once hooked,
this is the mother of all guides
Avoid David Day 'reference' books, though, as they're very pretty (well, the Bestiary is, anyway) but not accurate at all.
But if anyone is stuck for cash, just try the Encyclopedia of Arda website.