The Mahatma Letters to A.P. Sinnett is one of the books that is central to theosophical literature. I read, and reread it a lot, in the early years of my being involved with the Theosophical Society and it's one of the books I based my first online project on 'The Esoteric Studies Guide'. Joy Mills is famous in the Theosophical Society Adyar for her in depth study of these letters. She's been le…