Though his Hitch-hiker's Guide to the Galaxy series is widely known, Dirk Gently's Holistic Detective Agency and its sequel, The Long, Dark Tea-Time of the Soul, are not to be missed.

For fantasy of another sort, try Neverwhere, a fantasy/mystery set in the London subway system and the alternate world into which it opens. Also catch Stardust: Boy of uncertain parentage and dim future promises the prettiest girl in the village to bring back yon fallen star if she will marry him. She accepts the offer, but when he finally reaches the spot where the star landed, he finds instead a luminously beautiful and extremely grumpy young woman with a broken ankle. It seems stars change form once they reach the Earth... Both of these are by Neil Gaiman.

Phillip Pullman has written a remarkable trilogy that has been described as Paradise Lost for middle school, featuring a girl from an alternate Earth and a boy from this one. Absolutely stunning. The Golden Compass, The Subtle Knife, and The Amber Spyglass. They have the distinction of having been reviled by the Catholic Church for their subversive take on religion and deity, but the current flap over the otherwise harmless Harry Potter's embrace of wizardry has knocked the trilogy off the radar screen of most would-be censors.

All of you should find a copy of Youth In Revolt: The Journals of Nick Twisp, by C. D. Payne. It's not SF, but if laughter lengthens the life, this book has given me an additional 5 years. Amazon has excerpts to read here. Not for the delicate of sensibilities or the tender of years. It helps if you've listened to the complete works of Frank Sinatra. ;)

That's it for now, even though there's more.

Regards--
Mary Anne