Well as far as good books go a couple that I've read that are easy enough to understand with out getting obnoxiously technical are Good dogs, bad habits by Jeanne Carlson and Ranny Green. It explains how to teach the basic commands and has ways to help solve every behavior problem known in dogs. It's a great book and one of the first dog books I read.
Then there's Petspeak by the editors of Pets: part of the family. Another good book that covers dog behavior issues and even some cat behavior as well.
Dog tricks for dummies by Sarah Hodgson is also great. Not only does it teach you how to teach a billion different tricks it also explains how to tailor your training to your dog's breed, even mixed breeds.
If they want to try clicker training they can check out Clicker training for dogs by Karen Pryor.
If they have access to the internet have them check out Great pets
I hope this helps. Any other questions feel free to ask!