looking for a book that describes the different toxicity levels in reptiles

i am looking for a book or maybe even a web site that gives a break down of the different types of venom and the different toxicity levels of snakes and possibly other animals.
for example i am looking for something that pretty much rates snakes and other animals on their venom, kind of like how you see the shows and other discussions on what the top 10 deadliest snakes are, except i would like to find something that has all of the species broken down.
so far by doing a little searching i have found the "Clinical Toxicology of Venomous and Poisonous Animals", "Venomous Snakes: Ecology, Evolution, and Snakebite", and several others but the descriptions are rather vague and these are not cheap books, so i just want to make sure i spend money on what im looking for.
so is there anything book or website that any of you would recommend.

thanks