If you've played KOTOR & KOTOR 2 (and you damn well better have, or get out
), then Revan is a MUST!
I have yet to read Deceived, but I hear good things about it.
I liked Fatal Alliance just because, but it was hardly the best of them since it was mostly a thinly veiled excuse to introduce each of the character classes in TOR. I'm not even sure we'll see those characters again, in-game or elsewhere.