1. Children's books are told in pictures, not words. Pages of beautifully intricate visuals, with a few words or none at all. Have you read The Boy Who Was Followed Home? Every little detail tells the story. Or a story. That's why children's books appeal to both parents and children. What the child sees may not be what you intended, but it makes an impression on him.
2. Children's books appeal to the child's mind. It is illogical; it does not judge. To a child, all is possible. You do not need a "time machine" to go back in time. That is adult thinking. Children's books are surreal.
For example, the girl's loving father has cows in the house. A towering metal contraption with cows sticking out here and there, some tastefully decapitated. The girl watches a gruesomely obese lady with heavy makeup sitting in a restaurant, surrounded by stacked plates of pasta, pizzas, jellies, mac n' cheese, ice-creams. Eating everything. The obese lady reaches out one carb-dripping manicured hand to the girl, wanting to eat the little girl.
You create a world to tell your story. Don't fall over yourself trying to "teach" the future reader, but allow him to learn.
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With that said, here's what I like:
1. Patience and hunting. Magical bow-and-arrows for the girl?
2. Laura's archaeologist father-figure.
3. mkrnhr's hero archetype - yeah! Like the Narnia books - start with sick mother, return with healing apple. Shane's backstory too.
4. Ditto bngenoh and aurochs. Historical consistency > The Flintstones.
5. whitecoast, I agree! "Clues given out like an adventure mystery" - that's how children's books should be. About interaction between the two families: could it be a war instead? While the food war rages around her, the child quietly and calmly makes her choices.
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The thing about children's books is that there is no "cognitive dissonance." The main character in The Boy Who Was Followed Home never says, "This doesn't make sense!" Rather, he is surprised, hesitant, interested, and at the end, happy.