Yeah... to the tangental mention of Piers Anthony, have a second fair warning that dude's a bit a pervert (or at least writes like one, heh), and it infests pretty much everything he writes. Near as I can tell, just about every single book or series he's had published (at least of the stuff I've read, probably a good 1/2 to 2/3rds of his bibliography, which is quite a bit) has at least one sex scene (usually more) in them,
somewhere (including the Xanth series, which is ostensibly more child friendly.), and some of it can get a bit freaky (Firefly and Pornucopia, as examples, though everything else aside the latter has some pretty humorous scenes, at least as far as I got into it. Avoid Firefly like the plague.), even by my fairly lenient standards.
That said, he's fairly solid and the non-Xanth stuff that I've read is alright. I've got a bit of a nostalgia kick for the Adept series, Bio of a Space Tyrant has its up sides (
Down sides including rape and incest, among other things

), several of the Incarnation books are kinda' interesting, he's done some decent stuff if you can stomach some of his literary tendencies or the subjects they hit on (The Mode stuff hitting on suicide and some pretty decently fucked up gender stuff, iirc, as a general example...).
Definitely not on the same sort of scale as LotR and related materials, though.
Seconding the Riftwar stuff. I've got a couple of the books laying around somewhere, remember them being pretty decent. Incidentally, Riftwar formed the lore background for
Betrayal at Krondor, which is pretty neat in itself, or so I hear.