For people who retain better through cases and paragraph format, Case Files can be a very helpful supplement to your main study guide for internal medicine. The cases are very relevant and cover the basic pathophysiology, diagnosis, and treatment of a particular topic. I find the case/paragraph format and presentation of information to be very helpful in retaining information not only for the SHELF, but also for your actual rotation. The cases are short, easy to read, but full of pertinent and up to date information. This is the type of book you can read for 15 minutes and still get something out of, which may or may not be the case with main study guides.