I was using Notability and it let me have a preview of that, and I tried it on a ~40+ page reading I had for class. I feel like it worked well at picking out trivia (‘what is the definition of x’, ‘who did this thing’, etc), but it felt pretty shallow. If you’re preparing for a multiple choice quiz or refamiliarizing yourself with something then I’d say it’s probably okay, but if you’re studying for the essay portion of a test it’s not enough.