A query letter is what you send an editor in a publishing house which has open submissions (meaning they don’t have to come through an agent) OR to an agent, when you are attempting to interest one in your work.
Query letters should be highly polished, well-crafted, and short.
First, you need a hook.
Just like a book needs a good opening (think first 50 words for children’s books), the letter does too. Grab the reader’s attention!
Use “you.” That’s a perfectly legitimate rhetorical technique to draw the reader into a conversation with you.
Be careful not to complain with it though. “You probably wish the books you were receiving were higher quality.”
Also don’t ask questions they might answer with a “No.” Skip “Don’t you want a book that is true to the spirit of the Old West?” They might not.
Then you have to hang on to their attention.
Give a summary of the work, with details.
Including spoilers is fine. If this reader (or another like them) doesn’t take the book, no one else will have the twists and ending ruined by these spoilers. If they do, they won’t propagate that information out, because they want to sell the book, too.
Include author information.
Clearly and directly say what you as the author have in terms of relevance and authority. If you have already published children’s books, put this in immediately. After that, it gets a little more dependent on your personal experience.
Have you taught school to the age group? That counts.
Are you a long-time Big for Big Brothers/Big Sisters to folks in this age group? Include that.
If you played football all the way from Little League through college and your book is about football or is football-related, share your experience.
If you are an engineer for work and a horticulturist by hobby and the book is about plants, leave out the engineering information and focus on the hobby.
What information would I include?
I have taught this age group as an educator. (How long? Depends on what age group I am talking about.)
I have taught this age group once a week for years in a community setting. (For preschoolers to early readers.)
I have published a textbook as work for hire and have poetry published in various magazines and collections.
I have judged children’s poetry for cash prizes and publication for Abilene Writer’s Guild and the Art Young Poetry Contest.
Include contact information.
This seems “duh” but I am sure we would all be surprised by how often it is left off. Also, if you tell someone they can email you, make sure you check your email at least daily. You may have to answer a few spam calls, when your phone number is on your information. Make sure you give them a physical address to send information to, even if it is a PO box.