What to read after Secret of the Golden Flower?

This ancient esoteric treatise was transmitted orally for centuries before being recorded on a series of wooden tablets in the eighth century. It was recorded by a member of the Religion of Light, whose leader was the Taoist adept Lu Yen (also known as Lu Yen and Lu "Guest of the Cavern"). It is said that Lu Tzu became one of the Eight Immortals using these methods. The ideas have been traced back to Persia and the Zarathustra tradition and its roots in the Egyptian Hermetic tradition.