William G. Gray, better known to many as Bill Gray, was an English ceremonial magician, Hermetic Qabalist and writer, who published widely on the subject of western esotericism and the occult. Gray founded a magical order known as the Sangreal Sodality.
Librarian note: There is more than one author in the GoodReads database with this name
By far, this is one of the best books on the Sephiroth of the Quabala. Gray does an excellent job of breaking each Sephiroth down by planet, angelic order, archangel and god name association and explaining the Sephiroth in each of these levels. You'll also find that this book is easy to adapt to whatever practice you want to use to work with the Sephiroth. If you want to learn the Quabala, this is a good book to start with.
The Ladder of Lights is concerned with the Tree of Life (the Kabbalah). My copy is from 1971.
The book takes one through the process of climbing the Tree and understanding the levels - from the Kingdom to the Crown. It is full of very informative text but I personally found it a bit dry to work through at the time when I read it. It was not as stimulating as I had hoped.
It is intended to be introductory but I'd suggest one read Zev ben Shimon Halevi's book, The Way of Kabbalah first, and then come back to this book.
This book takes an often completely dense, unapproachable topic, and makes it not only relatively easy to understand (at least the absolute basics of it), but entertaining to read. I have not encountered a more readable book on the Qabalah.
Gray explained the four worlds better than any other authors I have read previously. Even so, it is so much information that I will have to reread it a few times.
A truly thorough and knowledgeable review into Western Qabalah, a slow walk up the ten Sephiroth as they are represented in the 4 Qabalistic worlds. This is much more information than my purpose, but a very simple and excellent read.