The Book of the Sacred Magic of Abramelin the Mage is actually composed of three books written by a person calling himself Abraham the Jew and is supposedly intended as a gift to his son named Lamech. It was supposedly written originally in Hebrew, but as of this date that original version is lost. The version we have of this book was translated by S. L. MacGregor Mathers from a 15th century French manuscript found in the Bibliothèque de l’Arsenal in Paris. The first book tells of the author’s adventures travelling the world looking for a master of magick. He is disappointed with the people he finds because they all seem to lack any form of spirituality. Finally, he meets Abramelin and believes he has found a true master. The second book prescribes the details of the ritual he was taught and the extreme demands placed on the aspirant to the magick. The goal of the magick to to achieve the "Knowledge and Conversation of your Holy Guardian Angel" who will then give you the secrets of controlling demons. The demons, thus controlled, will fulfill all of your desires. The third book is composed of cryptic letter squares, discovered as a result of the performing of the magick,  that have, supposedly, a wide variety of magickal powers. 

Here are some of the basic concepts presented in the book:

• Most magicians are mere demonologists with no concept of the Divine
• As part of this ritual you must focus intently, for a long period, only upon God
• This long, six month period of solitude, is marked by prayer, ritual, chastity, and similar practices
• This work results in meeting your Holy Guardian Angel
• With the information you gain from your HGA, you can make demands from demons
• These demands, made with the use of various symbols and signs, must be obeyed
• Because the practitioner has spent so much time becoming spiritualized in order to achieve these very worldly desires, it is likely that he will lose interest in them and, like many spiritual people, become detached from the world

While the book has limitations of it's time—it's sexist and advises against women performing this method—it is also very different from other magickal books of this period in that the focus on the Divine is paramount, not simply something added on as a cover to very non-orthodox religious ideas. The "rules" that are presented are more guidelines than strict dogma.

Aleister Crowley believed in the authenticity of this book. He made having a focus on achieving the Knowledge and Conversation of your Holy Guardian Angel a central principle of the lower grades of his magickal group, the A.A. The wording and concept has become a standard part of many magickal organizations.

The book makes clear that if you are going to start the method in the book, you must complete it. If you don't complete it the demons you wanted to control would have the upper hand and make your life miserable. Crowley began the ritual while he was living in Boleskin House on Loch Ness. However, he didn't complete it at that time (he did so later). There is nothing in the book that says interrupting the entire ritual is acceptable, though, and some people believe that the challenges Crowley faced with everything from poor finances to legal issues are the result of his interrupted Abramelin working on Loch Ness.