For someone who could barely put down the first two books in the trilogy, War of Three Waters was worth reading to finish the series but marginally satisfying on its own merits. Niles had a few fun, original ideas, but overall the plot tends more toward tired cliches and the romance falls flat--the Rudy/Raine, Takian/Bristyn and Danri/Kerri relationships were nearly interchangeable. My biggest problem was the glaring logical mistakes:
1. Rudy and Raine embark on their journey to Agath-Trol with the sword of darkblood, Raine explains to Rudy how to use it to teleport, Rudy comments that this could be useful, and the two proceed to spend the bulk of the book (what amounts to at least a couple of months) trudging around on foot. Coming across a river of lava completely perplexes them. How about actually using the teleporting sword they have in their luggage to speed up the journey before provisions run out? Naaaah...
2. Maybe Niles has never actually seen a dam, but he still should know that they don't stop rivers completely, they just control the flow. Whenever anyone constructs a dam in these books, the sheer force of all the rocks they throw into the river somehow manages to stop the river at its source...or something like that. A real river is going to either start flowing over it or find a new route, not just disappear from the face of the earth as these rivers seem to do. In Niles's world, this plethora of new dams doesn't even seem to create any new lakes.
The fast-paced action and sheer number of scenes Niles manages to include in this book will still please hardcore fans, but this book certainly could have benefited from a more critical editor.