(Obvious disclaimer: Not a doctor, not your doctor, this is not medical advice.)
For example, you treat a phobia through gradual exposure to the source of fear, not through undergoing a sudden overwhelming experience. That usually creates a traumatic response that actually makes the phobia worse.
Likewise, if you want to learn how to read a long book, start with shorter books and work your way up. If you can't sit through a novella and so you try to force yourself to read Crime and Punishment, you will fail — and you risk actually making it harder to read books in the future by strengthening the neural association between reading and feeling bored/frustrated.
These posts are arguing over 'scale' or degree. Everyone is agreeing on 'brain is plastic'.
Just arguing over starting with 'Crime and Punishment' or 'Snow Crash'.
I would just add, that it all depends on where the kid is at. This just jumped out at me because I did have one kid at young age, set a schedule and forced himself to read 'Crime and Punishment'. So it can be done.
But maybe for others, that is a huge step. Everyone is starting at some different levels of current skills, with different levels of drag. -- So any discussion here about 'where to start' will all be wrong.
I honestly love to read mathematical textbooks that are quite above my current mathematical level and knowledge. It is brutal to go through and attempting to understand the material, but this is soooo rewarding.
This method of learning mathematics is clearly not for everyone, but if you are sufficiently motivated to go this way, and love the brutality innate to this method, I actually would recommend it.