Zoe - while I am new to this particular forum, I have been "in discussions" with the Witness' for a couple of years now, both over the 'net and in person. I would suggest anything by Ron Carlson - he is a well respected author on cults in general and (for a more Christian apologetic approach) www.carm.org. They also have a wealth of knowledge on cults and their effects on people.
Good luck and God bless. You are in my prayers.
sezuhoo