In that case I [i]strongly[/i] recommend that LeGuin book. She's got chapters on everything from kicking an adjective addiction to pacing to expository lumps. It's something I still dig out when I'm struggling with a passage, and I've had the thing ten years now and must have done all the exercises a dozen times.

You may also want to check out Holly Lisle's site:

hollylisle.com

She's got a bunch of free articles up there -- many on the more practical end of things, but there's some on voice and such -- plus a store full of e-books, a link to the Vision e-zine (free), and a link to the Forward Motion writing community -- a great site full of helpful people. Holly's a good person, a good writer, and a fabulous giver of advice. :)

I know I have more resources somewhere. I'll post them if I think of them.