Knowing the Natural Law: From Precepts and Inclinations to Deriving Oughts by Steven J. Jensen is an excellent book on how an understanding of human nature leads to knowledge of the human good. The book focuses on how we can know the natural law. It does not apply the natural law to specific moral questions (e.g., is abortion permissible). 5/5 stars.
Here are some longer reviews:
The author also has a highly-rated book (which I have not read): Good and Evil Actions: A Journey through Saint Thomas Aquinas.