Robert A. Heinlein. Stranger in a Strange Land. Avon, 1967 (originally published 1961). 414 pages.
For the first couple hundred pages, it’s a very exciting science fiction story about a man raised by Martians coming to Earth. But about halfway through, the tension is abandoned and replaced with blather about how the secret to all happiness is to live in hippie communes and have sex with everyone you know. In addition to that dull, silly nonsense, the book is also sexist and (briefly but bitingly) anti-gay.