Hello aspirant

there is no particular book to study but your high school books or the last level of education you completed.

1. Start from the last 2 years of your high school book.
2. Prepare MCQs ( multiple choice questions)
3. Remember the reactions in the  case of chemistry ( very well)
4. Brush your English Grammar.
5. Prepare direct questions that can be solved in 2 to 4 lines
6. Do reasoning in the case of Biology. Don't expect direct questions here.
7. Formula based questions in Physics

There is no shortcut for MEX, you have to prove intellectually that you are the best candidate.