If the question is how to get the highest grades possible, then japhy may be right. However, if you want to build up your store of medical knowledge, you do that with textbooks. You do it with articles, conferences, reviews, and lectures. That's where you pick up the little, rare, random things that differentiate a good doctor from a great one. That's what you gives you the insight to see that an inconspicuous rash on someone's leg, taken in a certain context, is acutally a finding in 1-5% of patients affected w/ some random disease. Any and all doctors on the wards, from interns on up, should know the "high yield" stuff, the minor points or rare findings that get 1 or 2 lines in some huge textbook can separate them, and can make a difference in a patients outcome.
The point is, you have to do what you feel comfortable with. If you don't want to read big books don't, you won't retain anything if your heart isn't in it. Know what you've got to know cold, and the little things will fall into place.
If all doctors have the same basic "clinically important" knowledge, which they should, I'd want the one who went through 1000's of pgs of seemingly irrelevant but possibly one day useful material treating me.