I'm currently reading (slowly) The Magicians of the Golden Dawn: A Documentary History of a Magical Order 1887-1923 by Ellic Howe. The subtitle kind of gives it away -- it sounds like a thesis, and it is not the most exciting of reading experiences; but it does feel very factual, with dates pinned down and long quotations from letters written by the various major figures, so -- it is useful.
But looking for something more engagingly written on the same subject, I picked up my still-unread copy of The Autobiography of William Butler Yeats -- I bought it second-hand, most likely in a Half Price Books in Austin in the 1970s -- but it is one of those books (I have too many), bought on a whim, that I have carried around with me for decades without ever managing to read more than a random page or two. Today I thought I would just dip into it and see what Yeats wrote about his memories of the Golden Dawn. There is an index, but first I just opened it at random, somewhere near the middle -- the spine went *crack* -- oh, dear, it is well and truly broken now, between pages 226-227 -- and it was exactly what I needed to read, about one of the founders of the Golden Dawn, Macgregor Mathers, of whom Yeats wrote: "He like all that I have known, who have given themselves up to images, and to the speech of images, thought that when he had proved than an image could act independently of his mind, he had proved also that neither it, nor what it had spoken, had originated there."
The best thing I've read in the Howe book is from a letter written by Helen Rand to Annie Horniman on 10 October 1900, about a mysterious woman who called herself (among other names) Madame Horos. She was aged about 60, an American, and quite obese, although attractive. She "explained her great stoutness by saying she had absorbed Madame Blavatsky's spirit on the physical death of that lady and that had occasioned her swelling to such dimensions."