step up is key, first aid is the baseline you must know, it covers the need to know facts, memorization facts that is. Step up is much the same, but it takes a somewhat more clinical approach that really helps with step 1 questions. I would also highly recommend high yield histology and molecular biology. I think people tended to shy away from these two, but they are the two books I think put me over the top into the 99th percentile.
Step up has quite a few mistakes in it, but it is pretty solid. I liked Step up to the bedside. It has lots of vignettes and goes through differentials and then gives you some info on the selected pathophys.
i thought step-up was very repetitive with first aid BUT at the same time it was great for reviewing that same material in a different order during my last week of studying! i was so sick of looking at my overly marked-up FA that i wanted to barf, so it was nice to have lots of the same info in a different format to run through. i wouldn't say that there was much extra 'crucial' info.
Step Up is the one book that got me through the first two years. No joke - I used this obsessively. My copy is covered in notes. With that said - there are a lot of mistakes in it. It is also missing a lot of topics and is skimpy on lot of detailes. I wish that book had another 75 pages worth of info and I would pay $500 for that thing. For what it is right now - it's REALLY good.