on a somewhat related theme..
This is not directly Crowley related but does lend insight into a contemporary and sometimes rival:
I would recommend a read of Arthur Machen, Selected Letters (Aquarian Press 1988). This is as the title suggests, letters by the celebrated English writer of the macabre. -Author of such stories as "The Great God Pan" and "The Bowmen" , the later being probably his most famous work as it deals with the legend of the "Angel of Mons" in World War I.
Machen was one of the many Golden Dawners of that era. Interesting in itself, but the true gem of this work is the first section where Machen is writing to his old friend Arthur Edward Waite. It seems these two were quite close. Many intimate details of Waite's life are discussed (including a pet name of his mistress). By shedding light on Waite's character this provides some more of the back story of this period.