Oh... this thread is so huge I've had distinct trouble wading through it all and have given up prior to the end!
I thought I'd mention some of the stuff I've appreciated from my collection, apologies if they've been discussed before.
I think one of the great things about Tolkien is that once you've read the books, in my case at around the age of 8 or 9 I believe... They set you on a path of appreciating really creative, well thought out writing, in no matter what genre you prefer to wade. The downside to this (if you see it as a downside that is) is that it can make you a lot more picky about what you spend your money on... which sometimes can be somewhat frustrating when you've run out of current favourite authors and have to go looking for new ones! Here's some of mine, and I hope it might help anyone that is perhaps in that situation
William Gibson is a must for anyone interested in the more cyberpunk end of things.... he in fact pretty much created cyberpunk all on his own.
Neil Gaiman has been mentioned a lot here I note, but I thought I'd bring him up anyway, simply because he is probably the only author whom I can quite honestly say I find myself checking regularly on, to see whether there's been a new release... he is creating some incredibly unusual and enthralling stuff, not least of which were the Sandman series.
For those of you who are graphic novel fans by the way, I've recently started purchasing the Sandman spin off series Lucifer, which though not written by Gaiman is very much in his vein of thinking (think gods, devils, unseen universes, social commentary, dark humour). Well worth a read!
Oh and if you really want to find out where the origin of the wave of these sorts of adult graphic novels is, see if you can find yourself a copy of Watchmen... it was I believe the first of this kind, with a very unusual twist on the usual superhero scenario.
Orson Scott Cards "Ender" series is also well worth a read, another one with plenty of social commentary, set in a future galaxy where we're about to be destroyed by an alien race (or are we?) Sounds like a cliché I know, but very well written!
Shame the man himself is something of an outspoken character really…
I've not heard anyone mention the Dan Simmons Hyperion cantos which I'm quite surprised at?
And last but by no means least what about Peter F Hamilton? His night's dawn trilogy is stunning.... and you can't really fault any of the Minstar stuff (I forget the name of the series

) either.
Oh there's so many more!!!!!! I just love reading