Genetic Soldier occurs after The Destiny Makers but there's centuries between so GS can be read alone. 600 years earlier, the Earth is vastly overpopulated. A lot of fringe groups break out and one that becomes prominent is a Christian group of scientists who believe they must take steps to reduce the population. They develop a vaccine that they call something else, but really gradually reduces men's fertiity to nothing. They truly vaccinate the folks they want to stay fertile, so the fake vaccine won't hurt them. This happens in TDM.
GS starts with the ship Searcher returning from a 600-year-long search for a habitable planet. They find the Earth not only sparsely populated, but an artificial caste/village system has been set up. The secret rulers of the villages-- the Readers, Elders, and Ordinands -- don't want the ship to stay on Earth with its 300 scientists (plus 10 illegal children and three million embryos) and a verbal/physical/mystical contest begins.
I still like the book, although I once again thought it was odd that with 300 scientists, the ship was not able to man a defense. (The monopole mentioned was under scientific investigation when the book was written.) I definitely recommend this book.