[bermanoid]

I second these recs: all three are fantastic sources. MTW is very imposing (the damn thing must weigh twenty pounds), but don't be threatened, it is a crystal clear exposition that you really should not miss.

I'm not quite sure, though, if tel was asking for full mathematical developments of the theory (in which case the combo of MTW and Wald are, IMO, indisputable must haves), or something that just gets to the point quickly, assuming that you don't need help on the math.

In any case, anyone and everyone should also read Penrose's Road To Reality (my own shameless affiliate link: http://amzn.com/0679776311?tag=gubbins-20) for a very different take on...well, pretty much everything. The book is a complete failure at its stated goal of making mathematical physics accessible for a lay audience (I suspect when you're as smart as Penrose it's hard to figure out what an average Joe is capable of grokking...), but as a casual and wildly different sweep through a lot of interesting topics for someone that already knows math, it's fantastic.