It's something children's writers run into all the time -- the general public equating "children's book" with "picture book." But of course there are many genres, age levels, and types of books. I don't know about you, but I benefit from a review of categories and guidelines every now and then, because these things DO change. I've done some research as a refresher for myself, and found that there are no fewer than eleven children's and YA book categories. Let's take a look.
1. Baby Books -- These are for infants as the name suggests, and may be nursery rhymes, lullabies, books that picture and name common objects, or even wordless. Sometimes these are made of plastic rather than paper or cardboard, are very small in size, and viewed as "toy books" more than "real books."
2. Toddler Books -- Here is the beginning of simple stories of a child's everyday experiences or nonfiction topics such as colors, shapes, and so forth. Format branches out to include board books, pop-ups, or novelty books (those that make sounds, have die-cuts, scratch-and-sniff, etc.) Lengths usually top out around 300 words.
3. Early Picture Books -- For ages roughly 2-6, big sellers in this category may find a double life as board books. For example, Good Night, Moon. These books are shorter than 800 words, sometimes closer to 500.
4. Picture Books -- This the category most people mean when they use the term "picture book." These books are for ages 4-8 and traditionally contain 32 pages, although sometimes they have 40. Word lengths are usually around 1000 words. (The older 48-page format, at least for fiction, is pretty much dead, as is the longer "picture storybook" format that might extend up to 1500 words or so; you can still find the latter at a few publishers.) Topics, types of stories, and writing styles really start to branch out here, yet the pictures still tell at least 50% of the story. Most Caldecott-winning titles fall into this category. Nonfiction picture books can run maybe 2000 words, and may have that 48-p. length.
5. Easy Readers -- These books for about ages 6-9 have a more "grown-up" size and shape, but still generally have fewer than 2000 words and can be a lot shorter than that. They may be divided into "chapters" that are often self-contained episodes. Sentences must be grammatically simple -- simpler than in picture books, perhaps -- and usually written in a "ragged right" style, in which each line ends at a natural pause to aid comprehension. Publishers often subdivide this category into early, middle, and advanced easy readers.
6. Early Chapter Books -- Also aimed at about ages 6-9, these are written like easy readers yet are longer and reduce the illustrations to one every few pages instead of one per page or spread. A typical ms. for a book like this may run 20-30 pp. Plots depend on action and dialogue, not thoughts or psychological content.
7. Chapter Books -- Both age level and ms. length are growing -- about 7-10 and 45-60 pp. for these. Plots gain some complexity, but are still action-based. These books begin to employ cliffhangers at chapter endings. Chapter books are NOT middle-grade novels, which are described next.
8. Middle Grade Books -- These are traditionally for ages 8-12, and ms. lengths suddenly jump much higher. Largely because of Harry Potter, the general 25,000-word and 100-150 pp. in ms. length are now "floor figures" in the opinions of some. Lengths can and do get considerably longer. One or more subplots figure in. This is the age at which kids begin to fall in love with characters rather than just the action, and it's the age most likely to determine whether a child will become a permanent reader. Genres expand to include the gamut: historical, fantasy, especially humor; and nonfiction will cover just about anything a kid can be curious about. Most Newbery winners fall into this category, and a look at those will show you the sudden jump in sophistication level between MG novels and chapter books. Middle grade novels are NOT chapter books, which were described prior.
9. Upper Middle-Grade -- Also informally called "tween," this is a fairly new category aimed at kids ages 10-14. While there've been books designated for this age range for decades, the category is catching fire in the marketplace. Some Newbery contenders definitely straddle this category; think anything by Gary Schmidt, for example. As we might expect, kids who feel they've outgrown mid-grade but aren't quite ready for the "coming of age" and psychological/emotional concerns of YA readers will gravitate here. These readers want a peek into teen life, but from a bit of a distance yet.
10. Young Adult -- These books, usually for ages 12 and up, tend to deal with coming of age and the MC's inner feelings. The MC might be 15 or 16 years old and is likely to speak in first person. Nonfiction for YAs can cover subjects studied in high school or supplement it, typically in the broad areas of science or social studies.
11. Older YA -- For ages approximately 14 and up, older YA often crosses over with adult fiction these days. Some of these plots are grittier and carry the older teen protagonist, who is often 18, out from under the parental roof. Most restraints on adult behavior are lifted, and readers are assumed to understand a story on the same level of comprehension as an adult could.
Now -- I feel positively organized after all that! :) Which category is your favorite?