William Walker Atkinson is an old author that I discovered not too long ago. He writes masterfully on a wide range of metaphysical/occult topics. He also wrote under the name Yogi Ramacharaka and I just finished his book, "Science of Breath" and I enjoyed it immensely. His books are so old that they are no longer copyrighted so they are quite inexpensive. If you have not heard of him I highly recommend his reading material.