The orange board review book on sccm site will get you a pass on the boards. Their question book is good as well. I really liked Vincent's textbook of critical care, thorough and up to date yet very readable .
Orange book. Text is ugly as hell and there are close to no illustrations, but if you remember that ONE TABLE you'll get the polyarteritis nodosa question right on the exam. (!!!!!)
Second, and highly recommended (by me), is "Critical Care Study Guide" by Criner etc. A nice multidisciplinary review book, brief with appropriate diagrams and equations, that covers the whole range of knowledge in a good depth.