Like many homeless teens, Mathias died on the street. Unlike the rest, he came back-- as a vampire. [Leaving aside the inevitable vampire-genre ennui, this is an intriguing hook - if there's actually something about him being a homeless teen in the story and it's not just a device to make him a vampire.]
Transformed by vampires who believe him to be the reincarnation of an ancient king, Mathias learns that his new life is nothing like the legends. He has a new set of rules he must adhere to, and he's lived without rules for awhile. Although he now has the body of a powerful winged predator, he's still just a runaway. Plagued by visions of a past life, he no longer knows who he can trust. And when the revelation of his noble heritage brings him into conflict with the reigning vampire queen, who sees him as a threat to her rule, Mathias will have to grow up fast. Because if he doesn't, his second life may be shorter than his first. [My ennui has gone - this sounds like an interesting story and you've explained it clearly.]
RIDING ON THE TAIL OF THE DEVIL is an 56,000-word YA fantasy. [This could have come at the end of the opening para.]
My short story, “Papap’s Teeth” was published by Dailey Swan Publishing in February of 2010. [That's it? You're not going to tell me anything more about yourself? Like why you're writing a vampire story?]
Thank you for your time and consideration,
Overall: short but mostly effective. I did feel a little shortchanged though.
What you haven't mentioned: how your story is going to fit in the now enormous YA vampire-story genre - when you have this many competitors, you really need to think about how you're different and why an agent/publisher should take a chance on putting you in a very crowded market. Also, where is the story set? In the real world, or a made-up world?