Target audience and Word count:
Here’s a typical run down of manuscript lengths for different formats, taken from Darcy Pattison's Fiction Notes:
Picture book, including ABC titles. The hottest items are under 500 words. Some picture books can go up to 2000 words, but those are iffy. The audience for picture books can be anything from birth to about 10 years old. Usually the break down is something like 1-3 years old, 2-4, 4-8 or 6-10, though it varies from publisher to publisher.
The best advice for a picture book manuscript is “cut it in half.” Yes, it’s hard in 500 words to have a beginning, middle, end, a satisfying narrative arc, and a character that kids want to spend time with. Welcome to the difficult world of picture books.
ABC books, especially Sleeping Bear Press ABC titles, sometimes will go longer. But essentially the ABC format is just a way to organize information. These are not true ABC books for preschoolers.
Beginning reader and early chapter books. These are aimed at the beginning reader, so ages 4-8. For the truly beginning reader, the text may just be a couple words on each page. This is the only place where a publisher will try to control vocabulary, choosing words with regular spelling or from the sight vocabulary lists. By second grade, though, kids are reading short chapter books, and there’s more leeway in vocabulary and complexity of texts. These run maybe 6000-12,000 words, again depending on a publisher’s inclination and publishing program. Usually these are contemporary stories, grounded in a child’s real world.
Short chapter books. Some people add this category for 3-4th graders. These are short novels (novelettes?) of about 12,000-20,000 words. The topic of these books changes slightly to allow for historical fiction, science fiction or fantasy, or mysteries.
Middle grade novels. For grades 5-8, or about 10-14 years old, the middle grade audience has a wide variety of interests that are reflected in their fiction. Novels for this group run 30-80,000 words, but tend to fall more in the 40-60,000 range. Only the rare Harry Potter will go to 100,000 or more.
YA/Teen novels. For ages 12 and up, the YA or Teen novel has an almost free rein in length, complexity and subject matter. Still even here, the average novel might run 60,000 or so. You can go longer or shorter, if there’s a good reason for it. Some have said that YA novels are just like adult novels, just 100 pages shorter and without the sex scene. Today, you can add both the 100 pages and the sex scene. What distinguishes this literature is the tone of the story, particular the tone of rebellion of some sort. It’s a time of life when kids must break with their parents and figure out life for themselves; that’s what is reflected in the literature they embrace.
When I start to critique a manuscript and the cover letter states that the manuscript breaks the length/audience conventions, I start to worry. Of course, break any rule you want–as long as you do it well. But this is a major red flag in the concept and execution of a story. Have you matched up the audience and format?