I am an ATLS instructor, and i can tell you that yes, lots of people do fail ATLS. Yes, you should read the book before you take the course (there will be no time to read once you start the 2 day course). That being said however, most of the surgery and EM residents that take the course do pass. The "others" that take the course seem more likely to fail. Also, if you plan to take the instructors course at a later date, then you will need to score a 90% or higher on the written test, and will have to be deemed an "instructor candidate" by the instructors and be invited to do the instructors course.