It is similar to the NBME shelf that you took two months ago in that the questions are more clinical. The questions tend to be shorter, but are written in the classic COMLEX style. Be prepared for more than one answer seeming to be right. Be prepared to have a question describing something like epiglottitis and then seeing "there is no thumbprint sign on CXR." Who cares? He's got epiglottitis!
Four books. The first was easy - probably got >170 right. The second book was harder (I won't lie and say a little. It was harder.) Book three - well, you're exhausted anyway. Book four - the one with all the xrays, CTs, MRIs, EKGs, EEGs, etc. Most people I know were doing the xmas tree fill in for the last 50 questions of that book. Just so tiring.
Other than that, it's great!
Personally, I would take the longer-but-better-written-USMLE-step-2-any-day.