I have been lurking on this site since Feb. to help me prep for my test on July 28th; so needless to say, this is my first post. Anyhow, in response to your question, one book that I have found useful to determine CR patterns is the Kaplan GMAT 800, (2007-2008 Edition). Initially I was reluctant buying anything Kaplan for my studies because of a bad experience that I had four years ago with their GMAT class, (and also due to all the negative posts on this site about Kaplan), but I have actually found this book to be very helpful. It breaks down the types of CR questions, and helps to identify how to answer each question type. Before I bought this book I was scoring all over the board from a 60-88% hit rate. After studying with the book I have now been consistently scoring 90-100% of all the questions. Anyhow, my 2 cents. Good luck!