Wicca : Magical Beginnings

by Sorita d'Este & David Rankine
An extremely good introduction to the possible origins of Wiccan practices.

A Witches Bible
by Janet & Stewart Farrar
A classic introduction to British Traditional Wicca.

Ancient Mystery Cults
by Walter Burkert
A comprehensive introduction to the practices of ancient mystery traditions.

Craft of the Wise: A Practical Guide to Paganism & Witchcraft
by Vikki Bramshaw
A practical introduction to British Traditional Wicca and some elements of Initiatory Craft

A Short History of Myth
by Karen Armstrong