What to read after The Key to Theosophy?

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.