Marion Zimmer Bradley was writing before she could write. As a young girl, before she learned to take pen in hand, she was dictating stories to her mother. She started her own magazine -- devoted to science fiction and fantasy, of course -- as a teenager, and she wrote her first novel when she was in high school.

Given this history of productivity, it is perhaps no surprise that Bradley was working right up until her death in 1999. Though declining health interfered with her output, she was working on manuscripts and editing magazines, including another sci-fi/fantasy publication of her own making.

Her longest-running contribution to the genre was her Darkover series, which began in 1958 with the publication of The Planet Savers. The series, which is not chronological, covers several centuries and is set on a distant planet that has been colonized by humans, who have interbred with a native species on the planet. Critics lauded her efforts to address culture clashes -- including references to gays and lesbians -- in the series.

"It is not just an exercise in planet-building," wrote Susan Shwartz in the St. James Guide to Science Fiction Writers. "A Darkover book is commonly understood to deal with issues of cultural clash, between Darkover and its parent Terran culture, between warring groups on Darkover, or in familial terms."

Diana Pharoah Francis, writing in Contemporary Popular Writers, noted the series' attention on its female characters, and the consequences of the painful choices they must make: "Struggles are not decided easily, but through pain and suffering. Her point seems to be that what is important costs, and the price is to be paid out of the soul rather than out of the pocketbook. Her characters are never black and white but are all shades of gray, making them more compelling and humanized."

Bradley's most notable single work would have to be The Mists of Avalon. Released in 1983, its 800-plus pages address the King Arthur story from the point of view of the women in his life -- including his wife, his mother and his half sister. Again, Bradley received attention and critics for her female focus, though many insist that she cannot be categorized strictly as a "feminist" writer, because her real focus is always character rather than politics.

"In drawing on all of the female experiences that make of the tapestry of the legend, Bradley is able to delve into the complexity of their intertwined lives against the tapestry of the undeclared war being waged between the Christians and the Druids," Francis wrote in her Contemporary Popular Writers essay. "Typical of Bradley is her focus on this battle, which is also a battle between masculine (Christian) and feminine (Druid) values."

And Maureen Quilligan, in her New York Times review in 1983, said: "What she has done here is reinvent the underlying mythology of the Arthurian legends. It is an impressive achievement. Greek, Egyptian, Roman, Celtic and Orphic stories are all swirled into a massive narrative that is rich in events placed in landscapes no less real for often being magical."

Avalon flummoxed Hollywood for nearly 20 years before finally making it to cable television as a TNT movie in 2001, starring Joan Allen, Anjelica Huston, and Julianna Margulies.

Two years before she died, Bradley's photograph was included in The Faces of Science Fiction, a collection of prominent science fiction writers, such names as Isaac Asimov and Ray Bradbury. Under it, she gave her own take on the importance of the genre:

"Science fiction encourages us to explore... all the futures, good and bad, that the human mind can envision."