David Johnson & Frank P. Johnson 
Joining Together: Group Theory and Group Skills [PDF ebook] 
Pearson New International Edition

Joining Together introduces readers to the theory and research needed to understand how to make groups effective and, through exercises and thorough explanations, equips them with the skills required to apply that knowledge to practical situations. Chapters discuss the history of groups and group dynamics, the nature of experiential learning, group goals, communication within groups, leadership, power, decision making, controversy and creativity, and conflict management. More applied chapters focus on valuing diversity, cooperative learning, leading counseling groups, and team development and training.