Yes, the book itself is a resource. As to the points for discussion, if most of the participants are new to GTD, then it's best to concentrate on the workflow (mainly the second chapter) and project management (third chapter), both expanded in the second part of the book. OTOH if most people are using GTD, you may consider sharing their practices with each other, and more importantly to discuss the "perspective" aspect of GTD, which the book covers in brief in terms of the horizons of focus in the "Do" chapter. In any case, it is a good idea to have a few people who are into GTD for at least an year or so.
And a book like GTD can't just be read and discussed, so it would be nice if there are any followup sessions arranged.