You might also try Gordon Wheeler's book, *Gestalt Reconsidered*. He does a nice job comparing and contrasting Gestalt therapy with other modalities, and he also does a nice job in his critical grasp of some inconsistencies in the theoretical application of Perls and Goodman, as opposed to Lewin, when discussing field theory as "structured ground." In addition, he criticizes the catholic understanding of contact, proposing contact styles as opposed to the rather dichotomous contact/resistance model. The book is being reprinted and will have new introductory material in it, but you can probably find an older version in the library, or you can order one from Gestalt Institute of Cleveland Press.