I wouldn't say it's too early strictly because you don't have those classes. I'm assuming you're going to finish those classes before the summer you take the test (June 2009). It wouldn't hurt to study up on everything with your study books. I'm kind of hesitant to recommend doing any practice problems though. Yes, practice problems are key to success, but I think you should concentrate them about 3 months before you take the test. If you could get done with all the content review before that 3 month window, you will be in a good position. Doing the content review will also help you in those classes. So my advice, only do content review for now & nail it, read some journal articles/New Yorker/Economist etc to prep for verbal, and do an insane amount of practice problems & practice MCATs starting 3 months before you take it.