The Changelings: Summary

As those of you reading this blog may know, I've just about finished my first book, an 800-page epic fantasy called The Changelings.  As I prepare to submit to agents (or, failing that, self-publish), I've been trying to write a summary that will entice my audience while also capturing the essence of my novel.  This is what I've come up.  Let me know what you think.

Summary

What if your whole life was a lie? 

Sylvie of Brenton thought she knew who she was--the priest's daughter, an unassuming human girl content to lead an ordinary life.  But one sweltering summer day, her best friend Matthew reveals a long-held secret: Sylvie is a Changeling--a creature given human form and switched with the priest's real daughter.  And she's not the only one.

Four other Changelings lay hidden in the desert town of Brenton--including Matthew himself.  Once a child prophet, Matthew's premonitions of conquest and collapse prompted his people to create the Changelings--their one hope of survival.  Unfortunately, Matthew's visions were incomplete.  For seventeen years he waited to receive the end of the prophecy.  Now at last he sees the truth.

Matthew will die.  It's Sylvie who must finish the prophecy for him.

Heartbroken and confused, Sylvie tries to forget Matthew's words.  But the prophecy will not be contained.  Soon, the remaining Changelings set forth on a journey leading back to the place of their creation, where they will learn their true identities and confront their destiny.  And Sylvie--the only Changeling who knows the truth--must decide whether to uphold the prophecy that killed her best friend or abandon it altogether....