It is important to consider what one's goals are in practicing witchcraft. While some witches are religious, like myself, there are those who distinctly are not. Their secular witchcraft is no less valid then my religious practice. Indeed, it often has ties to the older roots of witchcraft that we will miss in contemporary readings.
For witches who are seeking to build a religious practice, it is important to start with the foundational materials. These teach where the concepts so popular in modern witchcraft originate. They also give the reader a grasp as to how these ideas can be worked with for maximum effect. For secular witches, the religious aspect of the information tends to be secondary to their interests, but it can be equally useful. Many of the earlier books on witchcraft included a great deal of information as to how the mechanics of the magical arts worked.
I highly recommend the following books on the basis of solid content on magical theory and theological considerations.
The Spiral Dance is one of the foundational books of American witchcraft. Starhawk very concisely and directly details the mythic history1of witchcraft under the guise of Faery Wicca. She presents a very pro-LGBT vision of Wicca. Her treatment of the genders is a bit dated (as of the 10th anniversary version, which I have on my shelf) but when taken in the context of the era that produced the work, it is exemplary.
Her rituals are very easy to comprehend and enact. Her detailed instructions on magical theory are quite accessible to the neophyte witch. The exercises that she presents are truly exemplary and I have found great success in using them with students in the past.
Author: Raymond Buckland
Buckland's Complete Book of Witchcraft is a meaty text that covers virtually any aspect of Wicca you could think of. It shows elements of Gardenerian traditional witchcraft, which Buckland was trained in, and of his Seax tradition of witchcraft that he developed upon his arrival in the United States. His treatment of gender divisions is more hetero-normative then that of Starhawk.
There is also distinctly less political overtones in Buckland's work. At the same time, he provides a great deal of information on a broad area of subjects. The information he presents is not entirely all inclusive but it is a good springboard for a student witch to use in determining what areas of the Craft they wish to study more deeply.
Author: Janet & Stewart Farrar
A Witches' Bible is a very through discussion of Gardenerian witchcraft. Janet and Stewart Farrar studied directly under Gardner (who is considered to be the father of British witchcraft and Wicca at large) like Buckland. Much of the information they present can cross correlate with Buckland's material.
At the same time, their treatment of matters of ritual procedure and the religious aspect of Wicca is far more complete then Buckland's. This is an excellent book for witches who are seeking for a more religious Wiccan experience.
There is the question of what of the witches who are not Wiccan, is there literature out there for them to read. There is of course material for non-Wiccan witches. I am not personally familiar with much of it, however. I can, though, direct you towards materials from other faiths that are useful to witches or any other person who is engaged in spiritual growth.
The writings of various Catholic Christian saints are the first thing that comes to mind. The works of St. Ignatius of Loyola, more specifically his spiritual exercises, can prove quite useful. When viewed as a series of intellectual and spiritual exercises that can be couched in the terms of what ever faith one follows, these simple and direct activities can help one harness significant mental and spiritual strength within themselves.
The works of St. Therese of Lisieux provides powerful instruction in spiritual growth. Her Little Way is exceptionally useful to both Christians and non-Christians alike. Her autobiography clearly illustrates how she implemented this practice and the influence it had upon her spiritual life.
The writings of the Protestant mystic Dame Julian of Norwich is both luminous in its spirituality and provides the reader with a strikingly clear path to developing a relationship with the divine. Her emphasis upon the maternal nature of the Divine and the loving relationship that can be established is one that is a refreshing contrast to the more patriarchal writings of the period.
Additionally, the work of the ever present age old author, anonymous, titled the Cloud of Unknowing can prove an extremely powerful tool in developing one's spiritual relationship with the divine. This text must be read within the cultural context of the era that produced it. Unlike the writings of St. Therese of Lisieux and Dame Julian of Norwich, the Cloud of Unknowing is much more difficult to translate to modern thought. Like the Zen koans, however, the Cloud of Unknowing can help one to experience the Divine by way of a juxtaposition of concepts.
1. I speak of the mythic history of Witchcraft because the history presented by Starhawk and various others is based in what evidence we have but can not be conclusively proven. As time has passed, the theories that had given rise to Starhawk's version of early history were called into question and I can not, with any academic integrity, state that this is a purely accurate factual portrayal of past events. Just because it is mythic, however, does not mean it is false.