player marks study chapters that will participate in the learning (maybe grouped in some way so people can choose one group as "active")
chapters are being presented to the player for study one after the other
some method of determining success (even asking the player how it went) will then increase/decrease/leave the interval until the same chapter will be presented
if the learning did succeed, the interval will double
if the learning fails after a success, the interval remains the same
two consecutive failures lead to a halving of the interval
It would work like this:
Still refining the idea