Quizzes work well for my daughter and myself. She'd rather do the quiz, every time. It's an action + a bit of knowledge (passive reading) = learning (memory).
My partner likes quizzes but he enjoys the competitive aspect to fuel his motivation. Me, I relate to what you just wrote above. Just different theories. But quizzes help both ideas. I actually prefer the quiz first, to help me read more efficiently, and then again, to further cement, but that's probably not the case for the majority, because it's extra.
The tracking comprehension is cool too. If you've got the backend covered, then curation of subject matter, categorization, and how it's written would be your biggest challenge, as you stated. Then navigation, UX design, pricing considerations, and good ol' marketing, which you've probably also considered.
Edited by cat-nips, 15 December 2018 - 09:38 PM.