When i was thinking of my top 5 sci fi books i realised I tend to read more fantasy novels, so lets do the top 5 with fantasy books. And just to make it interesting lets make it a J.R.R Tolkien free zone (regardless of whether you think he's up there or not). Here's mine in no order.

Eyes of the Overworld/ Cugel's Saga Jack Vance
Thomas Covenant Chronicles (1st) Stephen Donaldson
The Anubis Gates Tim Powers
Gormenghast Mervyn Peake
Cyrion Tanith Lee

How's that?
The worst Magician Raymond Fiest

These are just the top 5, there are many more Sci-fi/Fantasy books below #5.

1. The Hitchhikers Guide to the Galaxy:Douglas Adams (The whole 5 book trilogy)
2. Tomorrow and Tomorrow/Charles Sheffield (Straight Sci-Fi, no fantasy here)
3. Dirk Gentlys Holistic Detective Agency:Douglas Adams (All 2 and a half)
4. The Sentinel/Arthur C. Clarke (Actually Just his best short stories compiled)
5. 2001:A Space Odyssey/Arthur C. Clarke

Fantasy? Hmm. Some of my favorite fantasy is sort of Sci-Fi at heart, like Pern, which has dragons and a fuedal government, but is sci-fi in a pinch. If I remove books like that, (which also includes Ursula Le Guin's Left Hand of Darkness, unfortunately,) then my list is as follows.

1. Xanth by Piers Anthony. I love the first 6 books in the Xanth series, but I'd choose Centaur Isle as my favorite of those. It's light and frivolous, but I like it that way.
2. The Tree of Swords and Stones by CJ Cherryh (spelling?) A really wonderful Fey-Legend-based fantasy book, and it's companion, The Dreamstone.
3. The Taran Wanderer series by Lloyd Alexander. My favorite of those is The Castle of Llyr. Technically, I think it's for "young readers" but who the heck cares, right?
4. The Phoenix Guards by Steven Brust, and all related novels, including the Brokedown Palace (not related to the movie), 500 Years After and all the Vlad Taltos books. But Phoenix Guards is my favorite if you can get through it.
5. The Wizard of Earthsea by Ursula LeGuin. Don't recall enough sci-fi in this series to warrant removal from the list, and I can't choose which of the first three is best.

I haven't yet delved into Terry Goodkind or Robert Jordan. I've never read any Terry Brooks. I suppose I should. But except for Tolkien, I like my fantasy a little light-hearted. Other authors, like Mercedes Lackey and Susan Cooper don't quite make it onto the list, but are worth honorable mentions. So are a few TSR novels from my geeky D&D days. (Particularly RA Salvatore, who's non-TSR fantasy is making quite a splash.)

I've just cruised through my library of books and realized that I haven't read much since my kids were born (I have resorted to pinching their books when I have the odd moment). My favourites seem to run in writers of series of books or short story collections.
1- Ray Bradbury is probably one of the first writers I got hooked on, so to pick one - The Golden Apples of the Sun.
2- Kurt Vonnegut has a twisted sense of humour that I love - Slapstick
3-Anne McCaffrey has now been discovered by my daughter, I pass all the tales of Pern on to her. Yikes, to pick one, I'd say Dragonsong.
4-Sir Thomas Mallory wrote Le Morte D'Arthur and it is one book that I've read over and over since I was a tween.
5-The Mists of Avalon by Marion Zimmer Bradley, the Arthurian legend from a womens point of view.
(Can I sneak in a 6th- Douglas Adams and the HHGU)

Top five fantasy...
That's not really all that easy! Well, here it goes, in no order (cos that really is too hard):

A Storm of Swords (book 3 in A Song of Ice and Fire) - George R.R. Martin
Harry Potter and the Prisoner of Azkaban - J.K. Rowling
Night Watch - Terry Pratchett
Darkness at Sethanon - Raymond E. Feist
Revenge (Book 2 of the Trinity series) - Fiona McIntosh

Hrm.... these are not really in any order... and as you can see, I tend to get into books that are series rather than single volumes. You can get into the characters more when there is more time to get to know them.

*The Samaria series by Sharon Shinn (Archangel, Jovah's Angel, Alleluia Files, and Angelica).
*The Anita Blake series (and yes, I can argue it is fantasy, because it is set in an alternate reality).
*Time Enough for Love, To Sail Beyond the Sunset, and Stranger in a Strange Land by Heinlein.
*Mists of Avalon by MZB.
*You might consider these more Sci-Fi than fantasy, but I love the Honor Harrington series by David Weber.

I enjoyed the earlier works by Mercedes Lackey - the Vanyel trilogy, the Talia trilogy, etc. I've stopped reading her over the last couple years.

i like

Archangel (Sharon Shinn) {i picked it up in a secondhand bookstore and couldn't put it down... now i'm looking for her other books}

The Firebrand (Marion Zimmer Bradley)

and of course all the Harry Potter and Darkover books.

but hey, if you include sci-fi, i happen to be a Star Wars fan, and i'd also include Robert A. Heinlein's Revolt in 2100, Assignment in Eternity and Starship Troopers...

I'll have to echo two of Silver Moonsong's choices:

The Anita Blake series by Hamilton
The Mists of Avalon by Bradley
American Gods by Gaiman
The Discworld series by Pratchett
Good Omens by Pratchett and Gaiman

Here are my TOP 5 FANTASY BOOKS (exc. LOTR):

1. Harry Potter series by J.K. ROWLING:
The Philosopher's Stone, Chamber of Secrets, Prisoner of Azkaban, Goblet of Fire, Order of the Phoenix...

2. Obernewtyn series by ISOBELLE CARMODY:
Obernewtyn, The Farseekers, Ashling, The Keeping Place and The Sending which is yet to be released.

3. The Otori Trilogy by LIAN HEARN:
Across the Nightingale Floor, Grass For His Pillow and Brilliance of the Moon

4. The Legendsong Saga by ISOBELLE CARMODY:
Darkfall, Darksong and Darbane which is yet to be released

5. The Old Kingdom Trilogy by GARTH NIX:
Sabriel, Lirael, and Abhorsen

Hmmm well when you disregard Tolkien ... a lot already mentioned plus it's hard not to mention JRR for me so I will just add one :

Dark Materials trilogy by P. Pullman

Top 5 books ever:
1 The Discworld series
2 The Discworld series
3 The Discworld series
4 The Discworld series
and 5 The Discworld series

1. The Anita Blake series by Hamilton
2. The Mists of Avalon by Bradley
3. Harry Potter #5. by Rowling
4. Thomas Covenant Chronicles (1st) by Stephen Donaldson
5. The Avatar Series By Richard Awlinson

Maybe some could list their very favorite Terry Pratchett. Listing "Discworld" as one choice is interesting. I haven't read that many but am becoming an avid Pratchett fan. "Small Gods" and "Truth" are currently on my Palm reader and others are queued. I joined a "Meetup" of Terry Pratchett fans but we didn't have enough in Atlanta to make a MeetUp (needs 3). Pleasing to find so many here.
Jan

Love Pratchett too Susan (welcome to the site ), and if you haven't read Good Omes (jointly written with Neil Gaiman) then put it on your shopping list now! Didn't get to meet him but I have the first Discworld novel sighned which I'm pretty happy with.

All my top four fantasy favourites would be pratchett books. Good Omens first, second would be "Guards! Guards!" ("it's a million to one shot but it just might work" gaffaw gaffaw), the rest of them can fight it out for 3rd and 4th.

5th favourite fantasy would be Robert Rankin and the Brentford Trilogy series (can't pick just one)

If you've never heard of Rankin but are a Pratchett fan then you're bound to like some of his stuff.

Wow, thanks for the Terry Pratchett suggestions (could that have been quicker?). I haven't heard of Robert Rankin but now will check him out. And thanks for welcome - (my first forum post). Jan (Susan B.)

Would have been quicker if I could have remembered the name of the Guards Guards! book

Star wars BOBA FETT books are my fave.

Everyone has pretty much covered all of mine except one of Heinleins true fantasies, Glory Road.

Oh, "Glory Road"! Yes, a great book. In the same vein, has anyone ever read "Silverlock", by John Myers Myers?
An author to check out, for anyone interested in epic fantasy, is Tad Williams. His "Memory, Sorrow and Thorn" series is huge and wonderful.
George RR Martin has already been mentioned.
Terry Brooks' Shannara books weren't really to my taste, but some of you may enjoy them.
Those of you who just mention one author or one series, I would recommend that you branch out a bit, there is a lot of good reading out there - Robert Silverberg has edited a nice set of books called "Legends" that has long stories (or sometimes novel excerpts) from many fine fantasy novelists, set in their main fantasy worlds. It's a great introduction to these writers, and a good way to see if you would want to dive into a 600 page book, before you make the investment. I highly recommend it.

I enjoyed The Sword of Shannara but the rest of the series got a bit boring and repititious to me.

I'll cast my vote for C.S. Lewis' Space Trilogy:
1. Out Of The Silent Planet
2. Perelandra
3. That Hideous Strength
Beyond that, I love the Narnian Chronicles, Ray Bradbury, and H.G. Wells - particularly The Time Machine.

The Gate To Women's Country by Sherri S Tepper is unforgettable-if you're a woman you will love it.It's not really a book which will appeal to men.
Philip Pullman's-His Dark Materials (which has probably been mentioned on other forums)is a wonderful trilogy for all ages.
Most of Ray Bradbury's books especially Farenheit 451? (never can remember the number)

In no particular order:

• Terry Pratchett - Witches Abroad
  
• Margaret Weis and Tracy Hickman - The Dragon Lance Chronicles (really this is 3 books but I'm putting them together)
  
• Douglas Adams - The Hitchhiker's Guide to the Galaxy
• Terry Pratchett - Hogfather
• The Harry Potter books, but especially 'Harry Potter & the Order of the Phoenix'

~*Bee*~

Here are mine:

1. Servant of the Shard, by RA Salvatore

2. A Song of Fire and Ice (all three books, so far), by George R.R. Martin.

3. The Caves of Steel, by Isaac Asimov

4. Do Androids Dream of Electric Sheep?, by Phillip K. Dick (I also love many of his short stories)

5. The Postman, by David Brin. (Really an excellent story, don't pre-judge it based on your viewing of the Costner movie based on the book. They are two separate entities.)

hmmm, my top five.not in any particular order mind...

1.Blue Moon Rising - Simon Green

2. Icewind Dale Trilogy - R.A. Salvatore (Ok that is more than one book but I like Drizzt and Bruenor).

3.The Last Continent - Terry Pratchett

4. A Darkness at Sethanon - Raymond Feist

5. So Long, and Thanks for all the fish - Douglas Adams

My other half likes Sherri S Tepper. I am not a fan but funnily enough, the one book of hers that I like, he can't stand.