Acorna's Quest is a fantasy

Fantasy

Fantasy is a genre of fiction that commonly uses magic and other supernatural phenomena as a primary element of plot, theme, or setting. Many works within the genre take place in imaginary worlds where magic is common...

 or science fiction

Science fiction

Science fiction is a genre of fiction dealing with imaginary but more or less plausible content such as future settings, futuristic science and technology, space travel, aliens, and paranormal abilities...

 novel by Anne McCaffrey

Anne McCaffrey

Anne Inez McCaffrey was an American-born Irish writer, best known for her Dragonriders of Pern series. Over the course of her 46 year career she won a Hugo Award and a Nebula Award...

 and Margaret Ball

Margaret Ball (writer)

Margaret Ball is a science fiction and fantasy author who lives in Austin, Texas. Married and with two kids, she spends time writing, making quilts, embeadery, and taking care of kids at her home. She has a B.A. in mathematics and a Ph.D. in linguistics from the University of Texas...

. It is the sequel to their Acorna: The Unicorn Girl; those two were the first books in the Acorna Universe series

Acorna

Acorna is a "Unicorn Girl", a fantasy fiction character created by Anne McCaffrey and Margaret Ball in their novel Acorna: The Unicorn Girl ....

 that comprises ten books as of 2011. McCaffrey and Elizabeth Ann Scarborough

Elizabeth Ann Scarborough

Elizabeth Ann Scarborough was born March 23, 1947 and lives in Port Townsend, Washington. Scarborough won a Nebula Award in 1989 for her novel The Healer's War, and has written more than a dozen other novels...

 continued the series beginning with Acorna's People

Acorna's People

Acorna's People is a fantasy or science fiction novel by Anne McCaffrey and Elizabeth Ann Scarborough. It was the third book published in the Acorna Universe series initiated by McCaffrey and Margaret Ball in Acorna: The Unicorn Girl ; McCaffrey and Scarborough have extended the series through ten...

(1999).

Plot synopsis

Found as an infant drifting in space, Acorna, the Unicorn Girl, has become a young woman. She still has her tiny, translucent horn and her "funny" feet and hands. And she still has her miraculous ability to make plants grow and heal human sickness.
But Acorna has strange dreams of a gentle folk who mind-speak by touching horns. With her "Uncle" Calum, one of the three grizzled asteroid prospectors who rescued, protected, and raised her, she sets off to find her people. No sooner does she leave than a mysterious craft appears, piloted by the Linyaari, a gentle race with telepathic powers.
The Linyaari are roaming the galaxy, spreading the alarm about the deadly Khleev- and searching for a beloved little girl they had given up for lost, long ago...