H. P. Blavatsky 
Key to Theosophy [PDF ebook] 
Being a Clear Exposition, in the Form of Question and Answer, of the Ethics, Science, and Philosophy for the Study of Which the Theosophical Society Has Been Founded

Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. It is thought that a change of form in the mechanical con struction Of the book will be welcomed by most students, numerous complaints having been made concerning the size and generally unwieldy form of all the preceding editions.