1. Picture Books: ages 2 to 5. These contain little text and illustrations on every page. The stories have a clear single theme and a happy ending without much bad happening. Mostly the kids are curious at this stage and the stories that inform works well.
2. Picture Story: ages 6 to 9. More text, fewer pictures, much action in the story. These need to have a definite plot line, action that leads the main character to a goal. These are usually books read by an adult to a child. There needs to be a villain and the hero needs to be strong. Fights can be told but they should not harm the body of the hero.
3. Easy-to-Read, for ages 6 to 9 (grades 1-3), designed for children to read on their own. Book manuscripts will be 1500 to 10,000 words. Characterized by a definite plot line, a small number of characters, a strong hook in the first sentence, limited vocabulary, simple sentence structure. Here the success factor lies more in the story and how simple and short can it be told.
4. ‘Tween Age Books: ages 8 to 12. Many of these are books written for only girls or only for boys. Strong plot, clear characters. The story can have subplots, the description of the characters can deeper and the grey lines, between the good and bad can be written about.
5. The Teens: ages 10 to 15. Nearly any topic; boy-meets-girl stories are kind of done to death but many still sell. The scope for writing in this genre is immense. Fantasy can have any twist and turn, reality can be obscured, books can be in journal form (gaining popularity), laziness and not performing in school/college can be given a real interesting twist.
- Picture Book Writing Tips (kathytemean.wordpress.com)