The reason that books for toddlers lack chapters is that authors believe that toddlers aren't ready to comprehend chapters, not that it is an immutable truth of the universe that humans can't handle a separated narrative structure in writing until they've orbited the sun five or six times. Soviet children started Pushkin right when they started school- when I asked my Russian teachers for good examples of Russian children's books, they said that the concept didn't really exist when they were children, because they started studying real literature pretty much as soon as they started school.

The idea that there are "basics" that can be safely ignored once learned is patently false. Everything I've read from great performers in any field- piano, cooking, mathematics, physics, etc- contains constant encouragement to return to and refine one's understanding of the fundamental skills of the practice. I did indeed spend a long time practicing addition before anyone informed me that it was time to "move on" to multiplication, and it wasn't until I graduated college with a degree in aerospace engineering that I had read a few books about the history of mathematics and found out that the manipulation of Arabic numerals via "addition" or "multiplication" was simply shorthand for counting, which itself is a fundamental mathematical art. What was taught to me as "multiplication" is actually "one particular algorithmic notation for representing the counting of multiple sets", not "objective mathematical law".

Had I disabused myself of the notion that there was any part of mathematics that I could "stop thinking about" because they were "little", I would have made a much better showing in school.