Ways to use it
Bedtime
The book never runs out, and it stops where you say it stops.
A new chapter every night, in the right words for their age, that reads itself aloud when your voice has gone.
One chapter is the whole evening
A chapter takes a few seconds to arrive and a few minutes to read. That is the unit: you are not committing to a book, you are committing to tonight.
It reads itself when you have had enough
Every chapter has a read aloud button and four speeds. On the nights when you have been talking since seven in the morning, it takes over and you sit there.
Stopping is easy
The next chapter is a link rather than a scroll, so the end of a chapter is a real ending rather than a thing you have to tear them away from.