On Querying: Here's my query

Want to see the query that hooked my agent, who has now sold 6 of my books in four years and continues to help plot my career? Here it is!

Dear Ms. McKean,

I hope to interest you in SCRITCH, a middle grade fantasy/magical
realism complete at 43,500 words.  I follow you on Twitter, and I
assure you that this query was not written from jail, nor does it hope
to herald the next Harry Potter.  Although it would love to be the
next Labyrinth.

Twelve-year-old Lena Blackstone's baby brother screams every night,
and no one knows why.  That is, until Lena rescues him from a rat in
his crib-- a rat that bites her with unexpected fangs.  The next
morning, she discovers a teenage boy stealing socks in her attic.
Which would be terrifying if he weren't four inches tall.

His name is Selwyn, and he tells her that his people, the Scritch,
have lived in her family's isolated farmhouse since it was built.
What's more, the creature that bit her was actually a Gobbling, one of
the rat-like denizens of the basement.  His deadly venom revealed the
Scritch to Lena in their true forms. Unfortunately, it's also killing

But the truth behind her brother's screaming is even more sinister.
The ruthless king of the Gobblings wants to become human, and the
spell of conversion requires only one more ingredient: the heart of a
human child. He wants Lena's baby brother.

But he'll settle for Lena.

The first three chapters are attached.  May I send more?

Thank you for your time and consideration.

Best Regards,

Delilah S. Dawson

Of note:

1. You've never heard of SCRITCH, have you? Nope. Because it didn't sell. I had two agents offer representation and did several rounds of edits, but it just wasn't the right time for the market. And that's okay.

2. SCRITCH was my second book. My first book, FERRYTALE, was fatally flawed and now sleeps with the fishes. BLUD was my third book, and you might know it as WICKED AS THEY COME. Kate sold the Blud series at auction in a three-book deal. Yay, Kate!

3. There's a lot of discussion about whether or not you need an agent, and I am pro-agent. Very pro-agent. Have you ever looked at a 32-page literary contract? Yeah. Unless you're a lawyer, I always recommend going with an agent. They do so much more than sell your book.

4. I'm currently tweeting about querying and will storify those tweets on the blog afterward. Any questions? Ask!