What to read after The Key?

It is alleged that creeds tend inevitably to ossification; that the vitality of religions is almost lost itself in their development; that the ornaments of ritual serve only to obscure the Light which they profess to adorn and magnify Nothing, throughout history has been more painfully demonstrated than the barriers to brotherhood built up by religions; a rivalry often more fully emphasized than softened by missionary zeal Yet the Source of Spirituality must be One, even as God is One; and the differing languages and systems by means of which spirituality strives to assert itself, although they go far in the direction of perpetuating division between races and men, they have, after all, One common origin, the Word, lying dim and only partially realizable in the shadow of a time long-ago There are two minds, as it was written about the trees in the Garden of Eden, “The tree of the knowledge of good and evil and the Tree of Life” This Key determined these things specifically by discerning appropriate definitions in order to find out the sum of the whole matter.