Classicly

Married Love, or Love in Marriage by Dr. Marie Carmichael Stopes was published in March 1918 in England, was immediately sensational, sold out quickly, and was banned by the US Customs Service as "obscene." This book is essentially a manual for the sexually repressed married female of the turn of the last century. Stopes' ground-breaking work, which she thought would "probably electrify the country," is a not-so-subtle discussion of female sexual desire, with special emphasis on its correlation to "that time of the month." She also argued for equality between married partners, which was pretty hot stuff at the time. Married Love remains one of the most influential books of the 20th century.