The Wishsong of Shannara by Terry Brooks

Fans of the Shannara epic will revel as the forces of good battle an evil book, the Ildatch, which sends the Mord Wraiths to destroy mankind. To overcome this dark force, the Druid Allanon needs Brin Ohmsford, for she holds the power of the wishsong, a magic invoked by singing that can make plants bloom instantly or turn trees from green to autumn gold.

As Brin reluctantly joins Allanon on his dangerous journey, a prophecy foretells an evil plan to trap the unsuspecting Brin into a fate more horrible than death. But she has the help of her brother, Jair, and the protection of Rone Leah, who takes his job very seriously, as the comic rustics, Weapons Master Garet Jax and Slanter the gnome, leaven the fantasy.