"Married Love: A New Contribution to the Solution of Sex Difficulties" by Marie Stopes is a book published in 1918. One of the first works to openly discuss birth control, it sought to teach married couples how to achieve happy marriages and fulfilling intimate lives. Stopes explores balancing the desire for freedom and exploration with the constraints of monogamy and family life. Initially rejected as too controversial, the book became a sensation, selling nearly 750,000 copies by 1931 and ranking among the most influential books of its era.
Wikipedia page about this book: en.wikipedia.org/wiki/Married_Love