I have been researching occultism, religion, anthropology, etc. for over ten years, and this is the only book I have ever found that gives an adequate, accurate and concise explanation of the OTO, Thelema, & Crowley's Raison d'etre.
Anyone can build a website, but this book contains the Legal information, related to the OTO, Crowley's estate, etc.
The Bonus materials are good reading and make-up for the dryness of some of the technicalities involved in explaining the history of the OTO. This volume contains "The Book of The Law," clarifications about the religion of "Thelema," & Masonic / Templar connections to the organization of the OTO.
Anyone researching religion, occultism, "Secret Societies," Crowley, Thelema, Masonry, Anthropology or Sociology should definitely put this one on their wish list.
This is not the most exciting book you will ever read, but it IS crammed with information, in an easy to ingest format. Also, purchasing this book is like buying several for the price of one!