I've heard about books on residency interviews and while helpful, keep in mind that your interviewers know about them too. One faculty member told me that the year one particularly popular residency interview book came out, during the interviews, students were specifically asked questions that were not in the book and students were told to ask questions that were not listed in the book as "suggested questions to ask your interviewers". Isn't that crazy? Most likely an extreme example, but just something to keep in mind.