H. P. Blavatsky 
The Key to Theosophy [EPUB ebook] 

The purpose of this book is exactly expressed in its title, ‘The Key to Theosophy, ‘ and needs but few words of explanation. It is not a complete or exhaustive text-book of Theosophy, but only a key to unlock the door that leads to the deeper study. It traces the broad outlines of the Wisdom Religion, and explains its fundamental principles; meeting, at the same time, the various objections raised by the average Western enquirer, and endeavouring to present unfamiliar concepts in a form as simple and in language as clear as possible.