The popular and skilled urban fantasy writer Roxanne Longstreet was born on April 27, 1962, in White Sands, NM, and grew up in West Texas. She graduated with a B.A. in Accounting from Rawls College of Business at Texas Tech University in 1985. Her first novel, the fantasy Stormriders, based on the Shadow World role-playing game, was published in 1990 (and republished in 1996 under the pseudonym 'Ian Hammell'). She then wrote three horror novels and one thriller between 1993-1996, all under her original name.

After marrying artist Richard Conrad in 1992, Conrad then wrote two mystery-thrillers under the name 'Roxanne Conrad': Copper Moon (1997) and Bridge of Shadows (1998). In 2002, the thriller Exile, TX was also published under her married name.

2003 saw the debut of Conrad's writing career under her most famous pen name, 'Rachel Caine'. She published Ill Wind, the first of her popular Weather Warden series published by Roc from 2003-2011. The urban fantasy series, which ran in two series across 14 novels and several short stories, takes place on an Earth where a group of individuals called Wardens can control different elemental forces and use that power to protect humanity from natural disasters. The series' main character, Joanne Baldwin, is a Weather Warden, and the main series involves her adventures. An offshoot series, Outcast Season, concerns an outcast Djinn who seeks safety and a new life amongst the Wardens. In 2015, Caine launched a Kickstarter to fund a new novel in the series, entitled Red Hot Rain, but the book was unfinished due to Caine's health complications and her 2020 death.

Other series followed. In 2005-2006, Caine produced the two-book Red Letter Days series, an urban fantasy/paranormal romance about two female detectives who find themselves obliged to start taking cases from a supernatural client with their own agenda. From 2011-2013, Caine published three books in her Revivalist series, telling the story of Bryn Davis, a woman murdered by her pharmaceutical corporate overlords and revived from death via an experimental drug on which she now relies for continued existence. Her final series for adults was the best-selling Stillhouse Lake series of mysteries, starring Tennessee PI Gwen Proctor and beginning with Stillhouse Lake in 2017. The fifth book in the series, Heartbreak Bay was published posthumously in 2021 and was Caine's last published book.

Caine was no stranger to works of fantasy, science fiction, and horror for young adults. Her popular The Morganville Vampires series ran for 15 books, beginning with Glass Houses in 2006 and ending with the short story "Home" in 2019, was set in the fictional West Texas town in Morganville, a town owned by vampires as a sanctuary and where they live in uneasy tension with humans. The series was adapted as a web series in 2014 and lasted for one season, starring Amber Benson and Robert Picardo.

In 2015, Caine published the first in her YA alternate history/fantasy The Great Library series - Ink and Bone. The series is set in a world where the Great Library of Alexandria was never destroyed, and over the succeeding millennia has taken control of the world and the flow of information. Tne protagonists are several young Librarians who band together after discovering the injustice and tyranny behind the Library, and seek to bring it down through revolution. The series has five books, concluding with Sword and Pen in 2019. Caine co-wrote, with Ann Aguirre, another YA series - The Honors, a three-book space opera about a young woman named Zara Cole, who as an "Honor" pilots a living ship called a Leviathan along with her co-pilot Beatriz Teixiera. The first book in the series, Honor Among Thieves (2018) was named to the LITA Excellence in Children's and Young Adult Science Fiction Notable List for 2019. In addition to these series, Caine also wrote a YA standalone, Prince of Shadows (2015), a fantasy take on Romeo and Juliet.

Caine wrote several other standalone works as well, including Line of Sight (2007), a volume in the Athena Force series of novels about graduates of the Athena Academy, an elite school for girls with special talents, as they combat kidnappers, terrorists, and the forces of evil; a Stargate SG-1 media tie-in novel, Sacrifice Moon in 2007 (under the name 'Julie Fortune'), and a number of short stories contained in different science fiction, fantasy, and paranormal romance anthologies.

Rachel Caine lived for much of her life in Fort Worth, Texas, with her husband R. "Cat" Conrad. She was diagnosed in 2019 with soft-tissue sarcoma, and died on November 1, 2020. Caine was posthumously awarded the 2021 Kate Wilhelm Solstice Award for distinguished contributions to science fiction and fantasy by the Science Fiction and Fantasy Writers of America.