Are the 10 practice tests in the McGraw Hill 10 ACT Practice Tests (fourth edition) a good representation of a real ACT test or are they too hard? Easy? Is their study app a good and helpful resource or a waste of time?
MGH is on the easy side. In addition, it is the worse prep book.
So how many points should I take off my composite score? What are good prep books that you put recommend?
The red book, PR, Barrons.
Prep books are fine for learning content. They should not be used for practice tests (except the ACT Red Book). Part of the point of doing practice tests is learning the test itself and taking third-party tests does NOT help with that. No one else does a decent job of recreating the testmaker’s mindset in writing the questions even if they do test similar content.