If you are a student of the western system of the historic Golden Dawn, then this book would be a valuable reference book to have. A good reason to have this book is that for the most part, it was actually compiled by the Chief Adept of the original Golden Dawn, S.L. MacGregor Mathers.
As the story goes, it was entrusted to Allan Bennett, and Bennett gave a copy to Crowley during the period that they lived together. It was called The Book of Correspondences. This book is filled with tables and correspondences that include that of the original Hermetic Order of the Golden Dawn, where Crowley got his start, but also includes some non-Golden Dawn materials that Crowley added later after he left the teachings of the Golden Dawn.
I myself find it easy to ignore the swami and Arabic additions, concerning myself with only those consistent to the Golden Dawn. I am sure that most of the material came straight from Qabalistic materials that Crowley was given to study while in the Golden Dawn with his own little agendas added in, and this has been a point of contention since Crowley first published it in the early 1900's. Look past the parts that do not interest you. This book is a must for any practitioner of the original Golden Dawn system.