There are numerous books and stories that feature polyamory and non-monogamous relationships as a major, or at least a minor theme. We will be continually updating and adding to this section. Although these are works of science fiction and fantasy, and not necessarily written by people who actually lived polyamorous lifestyles, they nevertheless contain many interesting ideas and inspiring possibilities.
STRANGER IN A STRANGE LAND. This is the all time classic, by the widely acknowledged "dean" of science fiction, Robert Heinlein. Widely available, still in print after 40 years. Although, (so far as anyone knows), Heinlein himself never actually practiced polyamory, his ideas inspired a large number of his readers to attempt to create such lifestyles. The basic story of a human raised from infancy by Mars and then returned to earth has fascinated readers for generations.
GLORY ROAD: The book was the next thing Heinlein published following Stranger in a Strange Land. It was not well received, and never became popular. Closer to fantasy than to classical science fiction. The young Oscar is recriuted for a mission by the beautiful and magically talented "Empress of the known universe," and ends up with far more adventure than he had bargained for. Accustomed to thinking of Earth as the most important planet in the universe, and of the culture of the United States circa 1959 as the pinnacle of civilization, Oscar is stunned to learn that Earth is considered minor, almost trivial planet by the rest of the inhabited universe, and that the "civilization" existing in 20th century America is generally considered primitive, backwards, barbaric, and relatively uninteresting. Along the way, virtually every concept of what is natural, what is real, and what is "proper" is severely challenged,  most especially his ideas about sex, jealousy, love, monogamy and marriage.  Most of the main characters are not monogamous, and consider monogamy a peculiar idea. Although perhaps not the best of Heinlein's creation, it has it good points, and is worth checking out.
THE MOON IS A HARSH MISTRESS. Also by Robert Heinlein, and considered by some to be a superior work that Stranger in a Strange Land. This is a futuristic story of a revolution on the earth's moon, which has been made into a prison colony.  Many of the main characters are involved in various types of non-monogamous relationship. This is the book in which Heinlein introduces the concept of a line marriage, - a large group marriage that continues for generations as the older member die and new young members are continuely recruited.
FORBIDDEN TOWER. This work is a classic from Marion Zimmer Bradley, among whose other excellent works include the famous "Mists of Avalon." This is a fantasy tale of four-way romance involving a pair of twin sisters and two friends on a distant planet known as "Dark Over," that was colonized by earth people thousands of years in the dim past. The Culture of Dark Over seems to resemble medieval Europe in terms of technology and social structure, but in addition to extensive use of magic, the place has evolved a few of its own unique customs, such as the notion that it is a bad thing for any woman to give birth to more than one child by the same father, - which predictedly leads to some interesting family situations. While most of the rest of Bradley's large quantity of excellent work barely touches on the nonmonogamous themes, non-monogamy is THE central theme in this particular book.
2150 AD. Somewhere between science fiction and fantasy, this story, written by Thea Alexander about man from the late 20th century who suddenly finds himself mysteriously transported to a utopia society in the 22nd century in which the overwhelming majority of the population has transcended jealousy and possessiveness. Although many criticize the author's writing style and her somewhat "naive" new age ideas unappealing, the book continues to be "cult" favorite, and many have found the work highly entertaining and stimulating.
VIA POSITIVA. This is volume 1 of a two volume work by David SarBrooken, centered around the formation of polyamorous 'family" consisting of three men and one young women who refuses to be "owned " by anyone. An electronics wizard, a renegade psychologist and chemist accidentally discover a rapid and effective "cure" for jealousy. Although difficult to find, this is one of the more thought-provoking and outrageous pieces of science fiction to come along in quite awhile.
LOVE, - LIKE A NEVER FAILING FOUNTAIN. This is volume 2 of the story begun in Via Positiva.  The main characters of the previous volume inadverantly throw the business world into a quandry, caught between their greed to exploit the potential lucretive technology and their fear that the widespread use of such technology will evenutally destroy the social system that makes them rich and powerful. This book has the interesting feature of not only being highly entertaining, but also offering an interesting insight into why the church, the state and the rulers of society may be so terrified of polyamory and responsible non-monogamous relationships, why such people are so certain that the spread of such practices are so dangerous and threatening to "civilization," and hints at what might to done to change the minds of such people.
THE HARRAD EXPERIMENT. This interesting work is by Robert Rimmer, about an imaginary college in New England that encouraged sexual experimentation by its students, including such things group marriages. Although more about pre-marital sex at a time when even pre-marital sex was considered a radical concept, the book's open encouragement of non-monogamous relationship among young people captured the imagination of many. Published in the early 1960's, this was one of those widely read, much condemned books that inspired many and scandalized others. An excellent work. .