Frek and the Elixir by Rudy Rucker

It's pretty great. It's got the classic Rudy Rucker elements: cartoony action, but well-thought out connections. Heros who turn out to be pretty selfish. In structure it's straight out of "a hero with a thousand faces", which is really nice.

It has some hilarious parts, especially an alien race which has completely eliminated all variation in their ecosphere - there is only one kind of tree left, and one kind of animal, which they use for every purpose.

There are a lot of interesting ideas in this book.