From a major's perspective, I think there won't be anything you don't know, except for virtually Subject 5 (Introduction to Digital Forensics). Still, if you purchase it for a quick check to see if you've forgotten or are lacking in basic concepts for Subjects 1–4, plus as a summary for Subject 5, you won't feel like it's a waste of money. I prepared for about two weeks using this summary guide and the 'Digital Forensics Certification Exam Written Test' textbook. The written test textbook is not easy to come by (and feels like a waste of money to buy), so if you are a university student, it would be a good idea to check your school library.