Think of this as a source work. It outlines more-or-less the Alexandrian tradition, as it was practiced circa 1974, by the Irish Farrars. Stuart Farrar died a few years ago, and Janet has continued writing and publishing with her partner and co-author Gavin Bone. Back in the day, this was the only coherent book on Wiccan religion as it is really practiced within what the US calls "British Traditional Witchcraft" though when I was on your side of the pond, most old-school practitioners choke on the hilarity of such a concept as BTW (Gardner was a lot of things, but coherent wasn't one of them). You're not going to find much in the way of magic and spells as people have come to know them in the 90s; you're going to find religion, which is offputting to many.

The most valuable contribution of the Farrars are the books the Witches' God and the Witches' Goddess; it examines the archetypes most frequently used within Wiccan ritual construct and points out where these archetypes are linked to Wiccan theology.

Also, this site has long since replaced Why Wiccans Suck, and quite frankly has some real class to it, something that the aforementioned page did NOT have:

http://wicca.timerift.net/