CASPer has been compared to a written MMI. So they ask you ethical questions (usually you watch a video and they ask you how you would deal with the situation), questions about Canadian healthcare as well as questions about yourself (i.e. name and talk about your role model). You don't have to spend months preparing like the MCAT, but you should spend at least 20 hours or so preparing. I would recommend reading Doing Right as well as finding a book on MMIs, there may be books on CASPer already but if not, MMI is probably the most similar. I would also recommend doing practice questions and there are many resources online paid and not paid for this. The big thing with CASPer is you usually have 5 minutes to answer 3 questions and as a result, you need to practice your timing.