Feature request: It would be awesome if the interactive book had Index (maybe also Search) capabilities. Let me elaborate.
This index could be Alphabetically ordered keywords relevant to GMAT SC. For eg. that, which, as, like, pronoun, relative clause, prepositional phrase, it, etc etc etc. Now here is the magic trick - when one click on one of items in the Index, the app will show you all the relevant places in the Book that keyword is illustrated in the order of relevance. One can go to the 1st suggestion and there should have a link to the next relevant item, or something like that.
Currently, I waste some time to flip through pages to get to the part of the book I want to review. Sometimes, it is very annoying.
This feature can further be extrapolated to something like Search. But it is very important that it is not just any random (Lucene like) set of search results, rather these results should be relevant to
MGMAT SC book. This definitely needs a lot of work, or maybe not, but this will definitely be helpful to many; moreover, it will help engage your users