I've read many books on religion, and The Joy of Sects is a standout for its depth and breadth. History, sects, leaders, theology, terminology - all are made crystal clear for major religions such as Christianity, Buddhism and Hinduism, as well as for New Age and shamanism. Yet although the approach is exhaustive, it's not exhausting: the author manages to avoid the ponderous or slanted tone of many such books. The Joy of Sects is entertaining and even playful without in any way being disrespectful of or cynical toward any religion - a real feat in this genre. Highly recommended not just as an even-handed reference source, but for the pure fun of reading.
I have read this book probably ten times over the last ten years. It can be dipped into during a spare five minutes, or read cover to cover. It is fun and light-hearted, but not without providing lots of detail in a fair way. Even if you are a comparative religion scholar you will probably enjoy this book.