Tony,
Unfortunately there is no really comprehensive guide to deco theory. Most are either too basic for someone who wants more information or too advanced for the layman. Wienke's books although very comprehensive fall into this second category so don't worry if you find it heavy going.
The two books I would recommend are;
Beat the Bends - Alex Brylske
The Decompression Matrix - Bob Cole
Both are good on the basics but fall short on some of the more modern decompression theories such as bubble models.
There is also a lot of deco theory available on the web. I have tried to gather some of the best links together on my site.
www.dive-tech.co.uk/links.htm
If I ever finish typing up my notes to my intro to deco lectures .....