Have to agree with 1ke here. His book called “The good news about sex and marriage” is also helpful. West does a good job of making JPII understandable for us mere mortals.
I do note that the title says “human vitae” which is different than theology of the body. If you are looking for a book on Humanae Vitae or Casti Connubii I know Janet Smith has written a couple books. I don’t have the titles in front of me. I do find both of these encyclicals a little easier to follow than the audiences that make up theology of the body.