A few books I really enjoyed and would recommend;

The Man Who Folded Himself - David Gerrold
Not for kids- Time travel story about a man who receives a time travelling belt from a relative after his death.

The Worthing Saga - Orson Scott Card
My ALL TIME favorite book, I wish there had been some more books to follow it... I know there had been some bad press circling around Mr Card, not sure what it was about, but I wouldn't let that stop me from reading a good book.
I had lent my copy to a friend (who hardly ever reads any kind of books) and he LOVED it, he then lent it to his brother and got the same reaction, it went around to a few other people that way and I never got the book back.

I, Robot - Isaac Asimov
Collection of Asimov's short stories. This is THE book that sprouted my love of reading.

The Incarnations of Immortality - Piers Anthony
Fascinating 7 book series that tells essentially the same tale from 7 different perspectives, real page turner!

Dragonlance Series - Margaret Weis & Tracy Hickman
there have been MANY books based on the Dragonlance world, but the original (9?) books were really addictive! I have read a few of the other books, but most are written by other authors.

The Positronic Man - Isaac Asimov
The book that the movie "Bicentennial Man" was based on. Isaac can sometime be a tad long winded, but I highly recommend this book, especially if you enjoyed the movie.