When I was in school, I did a report on this, and the book I used that helped me the most was "Silent Waves, Theory and Practice of Lymph Drainage Therapy..." By Bruno Chikly.
I thought it was very "text-booky," (a little hard to read), but it had a wealth of information. He is one of the pioneers of the technique. (He improved on the techniques of Vodder...) It is not so much of a "how-to guide' as it is an explanation of the why's; the science behind it all. While he did give an overview of the techniques, he stressed the importance of in-class instruction.
Hope that helps you a little bit!