The Waterborn is a great fantasy book for adults. When I read The Waterborn, I was surprised how well it was created and written. It felt like a breath of fresh air, which was very nice.
The plot was good, the characters were interesting and there was enough depth. I think that Greg Keyes knows how to write about certain things (culture etc.) and he has a talent for charming his readers with his writing.
I think that The Waterborn is adult fantasy at its best. If you're interested in a not so typical fantasy book, you must read The Waterborn.