I'm a bit late posting this since I took the exam in May but it wasn't as tough as the CISM exam for me. Maybe due to CISM being more management focused. I leveraged only the ISACA CISA QAE database which I think is around $185 for members and $220 for non-members. It's great at providing explanations as to why the answer is the correct one and why the others options were wrong. If you have any type of experience in auditing you should be able to pass this exam.