A "lost ship" of Terran origin, in the pre-empire colonizing days, lands on a planet with a dim red star, later to be called Darkover.
1000 years after the original landfall settlement, society has returned to the feudal level. The Darkovans, their Terran Technology renounced or forgotten, have turned instead to free-wheeling, out-of-control matrix technology, psi powers and terrible psi weapons. The populace lives under the domination of the Towers and a tyrannical breeding program to staff the Towers with unnaturally powerful, inbred gifts of laran.
An age of war and strife reataining many of the decimating and desastrous effects of the Ages of Chaos. The lands which are later to become the Seven Domains are divided by continous border conflicts into a multitude of small, belligerent kingdoms, named for convenience "The Hundred Kingdoms". The close of this era is heralded by the adoption of the Compact, instituted by Varzil the Good. A landmark and turning point in the history of Darkover, the Compact bans all distance weapons, making it a matter of honor that one who seeks to kill must himself face equal risk of death.
The renunciate stories take mostly place after the Rediscovery by the Terrans
During the Ages of Chaos and the time of the Hundred Kingdoms, there were two orders of women who set themselves apart from the patriarchal nature of Darkovan feudal society: the priestesses of Avarra, and the warriors of the Sisterhood of the Sword. Eventually these two independent groups merged to form the powerful and legally chartered Order of Renunciates or Free Amazons, a guild of women bound only by oath as a sisterhood of mutual responsibilty. Their primary allegiance is to each other rather than to family, clan, caste or any man save a temporary employer. Alone among Darkovan women, they are exempt from the usual legal restrictions and protections. Their reason for existence is to provide the women of Darkover an alternative to their socially restrictive lives.
After the Hastur Wars, the Hundred Kingdoms are consolidated into the Seven Domains, and ruled by a hereditary aristocracy of seven families, called the Comyn, allegedly descended from the legendary Hastur, Lord of Light. It is during this era that the Terran Empire, really a form of confederacy, rediscovers Darkover, which they know as the fourth planet of the Cottman star sytem. It is not apparent that Darkover is a lost colony of the Empire, until linguistic and sociological studies reveal that Darkovans are of Terran extraction-a concept not easily or readily acknowledged by Darkovans and their Comyn overlords.
With the initial shock of recontact beginning to wear off, and the Terran spaceport a permanent establishment on the outskirts of the city of Thendara, the younger and less traditional elements of Darkovan society begin the first real exchange of knowledge with the Terrans-learning science and technology and teaching Darkovan matrix technology in turn. Eventually Regis Hastur, the young Comyn Lord most active in these exchanges, becomes Regent in a provisional government allied to the Terrans. Darkover is once again reunited with its founding Empire.
These volumes of stories, edited by Marion Zimmer Bradley, strive to "fill in the blanks" of Darkovan history and elaborate on the eras, tales and characters which have captured readers' imaginations.
MZB has mentioned that it is not absolutely necessary to read the books in chronological order, since they mostly stand on their own. However, I do think that particularly the last books, that were only recently published are better read in order. For those who are interested in the development of a writer, read it in the order they were published, which in the end coincides with the chronological order anyway.