The author does a fine job of combining analysis with synthesis, and he incorporates into his historical overview a generous sampling of the stories of a significant number of major characters. Perhaps the greatest achievement is Karamustafa's skill in making an immensely complex and potentially amorphous topic understandable. He manages to weave together very accessibly strands of history from diverse cultural and historical contexts across the central middle east, but the narrative remains concrete and avoids indulging more than necessary in discussing 'theoretical' issues. This is a very thoughtful treatment and I believe it will make a wonderful contribution toward a more integrated, comprehensive understanding of one of the most interesting subjects in late antique/early medieval Islamic religious history."--John Renard, St. Louis University