Definitely purchase the full HESI A2 version (for $25), you will NOT regret it. The app pulls information directly from the Elsevier Exam Review. You can get an insight and feel for how the test will be like if you study the questions off of the app. And yes, there are many questions in the app that the book does not go over. If you get a question wrong, they will tell you why/how so next time, you can get it right. I used One Note to transfer all the questions/terms/equations I didn't know and studied like that. I was told the Elsevier book was enough but to my standards, it was not. Best wishes.