'Natural Law in the Spiritual World', written in the 1800s by Henry Drummond, delves into how the natural laws of the universe apply to the world of spirit. The book presents spiritual insights in an easy-to-understand manner, making it accessible to readers of different backgrounds. There are chapters dedicated to topics such as biogenesis, abiogenesis, degeneration, reversion to type, and more. The book may be a little wordy in places, but it is spiritually poetic and beautiful. Ultimately, it provides insight into the importance of God and the eternal nature of the soul.