I’m probably not the only person here that is pursuing the official MongoDB certificates. While the courses are lovely, nothing beats having the official cert on your resumé.
May I suggest opening a sub-forum for exam preparation discussions? A place for students to trade book reviews or to help each other along with particularly confusing subjects. Of course reddit.com/r/mongodb and TechExams.net are good discussion forums, but I could also see it adding a bit of value to your local MongoU forums.