I second the vote for "Click to Calm". You'll probably have to order it from www.dogwise.com
( I love ordering froma amzon because of teh free shipping and low prices) It's not readily available in stores-- at least not near me.
I would also consider Pam Dennison's books about aggression. She's wonderful. I think the title of the one I would get is "How to right a dog gone wrong". "Bringing light to Shadow" is wonderful too- but not so much a 'how to' book as a story about her own aggressive dog.
in the mean time some great very short articles on aggression by Suzanne Clothier can be found at:
A couple of other books just about dogs and positive method training in general that I love and think every dog owner should read are "The Culture Clash" by Jean Donaldson and "The other end of the leash" by Patricia McConnell.
Emma Parson's has a "Click to Calm" yahoo group that you might want to check out too. I've heard it's wonderful and very supportive-- the moderator is someone who works with Emma in her reactive dog class.