If you find a good book, go for it, but I don't think it's necessary at all. Let's face it, you can think of some biggie ethics questions in advance (how do you feel about X law? what would you say to a client of an HBC dog that doesn't have any money?), but it's such a HUGE and broad area. My advice is to think through as many example scenarios as you can (or just start paying attention to each case you see if you work at a veterinary hospital) and start formulating your own opinions. It's my impression that the interviewers don't care so much what your exact opinion is - the many varied viewpoints in each veterinary class makes it clear that they aren't selecting just for the folks that agree with all the AVMA points. They just want to know that you have thought about your viewpoints and are willing to stand by them. So if they ask you an ethics question, you give your answer and then they start poking and prodding and asking more questions about it, it doesn't mean that they disagree or think your opinion is wrong, they just want to see if you are willing to stand by it and why. I think that ethics questions were the ones I worried LEAST about because I knew they DON'T have set answers - just know what you believe, think carefully about the question and then say what you think and stand by it and you'll be fine.