Will the interview try to trick me?

The simple answer is no. They will never try to trick you. The reason why Oxbridge interview is so that they can get a real sense of passion for your subject, which doesn't always come across on paper. So go in, be yourself and think about their questions critically. You will have to read up before your interview - know the books you mention in your personal statement, have an idea about the most influential literature for your subject. Before you answer: repeat the question in your head; take a deep breath and go for it.