I've read most of her books. She comes under the sci-fi/fantasy genre, though after the first book it becomes mainly sci-fi.
She's written:
The Ancient Future Trilogy
-The Ancient Future
-An Echo in Time
-Masters of Reality
The Celestial Triad
-Chronicle of Ages
-Tablet of Destinies
-The Cosmic Logos
The Alchemist's Key
And there was another one that I can't remember the title of and I haven't read.
I rather liked the Ancient Future Trilogy and the Celestial Triad, since the latter was a continuation.