A relatively--no, decidedly--mediocre fantasy novel by the otherwise talented Jane Yolen.
Very clearly a children's book (and not a "children's novel" in the sense of The Hobbit or the Narnai Chronicles), it in no way compares to most of her other works, such as the Pit Dragon Trilogy.
However the book is interesting in two points--its very good explanation of the concept of truename, and its use of a wizard whose only talent is the ability to enhance other caster's spells. The character is barely able to cast spells on his own, but creates a 'resonance' that amplifies other wizards' power incredibly.
Worth a read if you have nothing better to do, or really like Yolen. It's certainly a lot better than most of what passes for "children's literature" these days, but don't expect too much from it.