I wouldn't worry about casebook questions, they are usually too vague and too hard at times. Hell, dont worry about cases. Most of the time you need to know a sentence or two about the essential holding. Nothing more is needed, because you will pretty much never get a question about the facts of the case, or the reasoning per se. I was top 5% my first semester (still waiting for grades now) and to be honest, casebook studying took up probably 10% of my time depending on the cold calling system. If we had no cold calls, i would skim over cases really fast and would read about them in hornbooks to get a better idea.
Looking back at some specific classes. In torts our prof assigned the entire casebook cover to cover. I maybe read for the first few weeks and then stopped entirely. I got an A on the exam, the highest grade he gave out that semester. Same with Civ Pro. I got called on once, didn't know what the hell the facts of the case were about, looked like an idiot to everyone else... still got an A, again the highest grade given. Contracts was different because we had tough cold calls, but even then i stopped reading once our prof stopped calling. Again, got an A. I think you can get the idea... I think the only class where I think you need to read cases is Con Law, and even there you can go buy reading hornbooks and case summaries.
To be clear, i'm not saying blow off class and cases. I knew all the major cases, knew all the holdings and the arguments given. The only thing is that i read about them in a time saving manner- in hornbooks and etc. Anyhow, my 2 cent.