Ack! No Piers Anthony or Douglas Adams??? I see, Danielle Steel is WAY more important!
Most of my favorites have been mentioned but I see that Charles de Lint is missing—prolific modern Canadian author who writes urban fantasy/mythology stuff. Also, I assume you have H.P. Lovecraft somewhere in there, right?
A great anthology series: The Year’s Best Fantasy and Horror edited by Ellen Datlow and Terri Windling.
…and for young readers, look for John Christopher’s sci-fi novels, C.S Lewis’s Chronicles of Narnia, and Madeleine L’Engle’s A Wrinkle in Time, A Wind in the Door and A Swiftly Tilting Planet.
For adults, another excellent and favorite fantasy trilogy of mine is by Joyce Ballou Gregorian: The Broken Citadel, Castledown and The Great Wheel.
Stuffy - Really? The books were fantastic up until the super-dooper, flippin-flooper, I-ran-out-of-ideas-or-couldn’t-match-my-own-hype-and-caved anticlimax. Although I give credit to Hamilton for finally outdoing Frank Herbert in creating a believeable (and more interesing) space opera setting. Get a chance to read Second Chance at Eden? I wanna see another story about the renegade Edenists, the “Serpents”, or at least find out what Laton is up to.
Whoa… Andre Norton is a woman?
I agree with the idea of getting the popular and well known stuff first, then go for the good stuff. (not to say there isn’t an overlap there)
Everyone I was going to suggest is already on the list here… though I’m surprised to see someone recommend that awful hack Fred Saberhagen :barf:
This thread from a while back contains a lot of ideas as to what constitutes an “essential” SF collection. Lots of titles, and people explaining and justifying their choices, and not all that much pointless flaming. (I’m still ticking off items on Fenris’s final list.)
Yeah, true he did, but them so many great books finish badly that I’m a little forgiving. I felt the same way about Battle Field Earth, it was great until those last 20 or so pages. I keep hesitating picking up SCE, I want to read it, but well there’s that ending thing 
I read somethng somewhere that implied Laton and the characters from teh series wouldn’t be in it, but I can’t remember where I read that.
Well, I’m not going to bother mentioning any specific books or authors, because you already have a huge list here. But I will say that good, well-written science fiction and/or fantasy is pretty hard to come by. There is a lot of crap out there.
Take Piers Anthony, for example. Very much a hack writer. Which is not to say not-entertaining – his Spell for Chameleon was pretty good if you don’t mind characters and dialog that leave splinters. But he sequeled it to death and some of the sequels were mighty bad.
I’d avoid Star Trek novels and cookie-cutter fantasy novels (cough Terry Brooks cough) that have intrepid heros going off to slay dark lords. Fantasy novels violate Sturgeon’s law in that vastly more than 90% of them are crap.
Oh, I’m not sure anyone recommended Peter S. Beagle, so I would recommend that you get his The Last Unicorn and A Fine and Private Place.
Well, I’m not going to bother mentioning any specific books or authors, because you already have a huge list here. But I will say that good, well-written science fiction and/or fantasy is pretty hard to come by. There is a lot of crap out there.
Take Piers Anthony, for example. Very much a hack writer. Which is not to say not-entertaining – his Spell for Chameleon was pretty good if you don’t mind characters and dialog that leave splinters. But he sequeled it to death and some of the sequels were mighty bad.
I’d avoid Star Trek novels and cookie-cutter fantasy novels (cough Terry Brooks cough) that have intrepid heros going off to slay dark lords. Fantasy novels violate Sturgeon’s law in that vastly more than 90% of them are crap.
Oh, I’m not sure anyone recommended Peter S. Beagle, so I would recommend that you get his The Last Unicorn and A Fine and Private Place.
In addition to those named, many of which I endorse, I’d add Poul Anderson, Lois McMaster Bujold (who is the only writer ever to approach Heinlein in terms of number of awards won – but skip her two fantasies), and John Barnes (the three books from the 1000 Cultures series are outstanding).
And for the adults, his space trilogy (I forget the titles).
I haven’t read any books of Night’s Dawn caliber that failed so miserably in the end. Almost all reviews mention how unforgiveable the ending is. Re: Second Chance at Eden. It’s a collection of short stories all concerning bitek. It relates some of the earliest uses of it and the galaxy’s first reactions. I particularly liked the title story and Candy Buds. You get some background on J. Calvert’s father and the Lady Macbeth and there are several references to events and places in Night’s Dawn. Good, not great, reading. I thought Laton (as the rare free-thinking Edenist) was the most interesting character of the series and thought he should have played a much bigger role, such as coming in at the end and leading humanity to victory over the… uh… okay, no spoilers here. Short hijack over.
Unfortunately, it’s likely that most of these are out of print. Find them anyway!
Anything (‘everything’ would be better!) by Cordwainer Smith would be good. Or maybe ‘great!’ would be the right word. (Am I frothing yet? 
) SF, but like nothing else you’ve ever read in any genre.
For fantasy, a couple of old ones:
The Gormenghast trilogy by Mervyn Peake is wonderful. Castle Gormenghast is the real star here, though Titus Groan is the nominal hero. What can you say about a series in which the protagonist isn’t even born until the end of the first volume?
The Kai Lung books by Ernest Bramah are fascinating too - stories set in a classical China as imagined by 1920s Westerners. Funny and more!