Systems of Psychotherapy by Prochaska and Norcross. It is a healthy sized textbook with each chapter devoted to specific branches of psychotherapy (e.g. humanistic, CBT, psychoanalysis, feminist). The authors offer you the main ideas behind each theory, how they would work in practice, and at the end of each chapter is a commentary that contrasts the theory you just read with other theories and 'argues' each point of difference. Lots of good research citations as well.