There are only two other book sources on r/c subs that I am aware of:
"Model Submarine Technology" by Norbert Bruggen. I've not read it but I understand it is comprehensive and can get pretty technical. Norbert is a highly accomplished model submariner. You can buy it through Amazon.
"RC Submarine Modeling for Dumb A**es" by Steve Neill. This is a CD-Rom photo tutorial of Steve's scratch building projects. You can learn more about it here: http://www.sneillfx.com/page23