The Nature religion of Wicca is developing and evolving at a surprising rate. Initially created as a reconstruction of the pagan "Old Religion", the Goddess-worship/religious witchcraft of ancient history, Wicca has had a hard time making itself accepted in a society brimming with religious bigotry, dogmatism and prejudice.
Taking advantage of today's (slightly) more tolerant outlook, this book presents many of the basic tenets and practices of various Wiccan traditions, complemented by the inclusion of the author's own Book of Shadows as a personal point of view. It provides a basic overview of the ideas behind the ritual, the mechanics behind the magic, and the issues that need to be considered by those walking the Wiccan path.
Those keen to know whether this is a "better" or "worse" book than Buckland's "Complete Book of Witchcraft" would, I think, do better to consider it simply "different". Cunningham's approach is not to handle the reader as his own student, as Buckland does, but to provide general information and answers on non-tradition-specific questions which might be asked by the newcomer or the simply curious.
Like Buckland's "Complete...", this is not a "spell book" for those raised on a pop-culture diet of "Charmed" and "Sabrina the Teenage Witch" - look to Titania Hardie for those - although neither is it solemn or grave. Wicca is, after all, a celebration of life. But to get the most out of this book, as with so many others, it's important that you are able to treat Wicca with the respect due to all religious traditions.
Overall, this is a fine reference tool, as well written and much more freeform than Buckland's "Complete..." - you can dip into this book more or less as you please, rather than having to work through a set curriculum. For those looking for general information rather than a specific course, this is ideal.