You would be wasting materials completing them without a strong foundation in math/science (e.g., College level Bio, Chem, etc). That being said, it's never to early to start preparing for verbal reasoning (or whatever they call the equivalent on the 2015 MCAT).
I would recommend you start reading op-ed articles and other forms of dense prose on a (somewhat) daily basis. Washington Post, NYTime, Economist, whatever. Read for pleasure. But also be sure to pick out articles that you find boring. Train yourself to remain attentive...many people tend to read the intro, go autopilot through the body, and finish on the conclusion without gaining insight on what the article is really about (Think: topic, scope, purpose, author opinion, etc).
The more familiar you become with dense prose, or reading things that are uninteresting to you, the better you may become at interpreting and digesting MCAT passages. Also...you will gain some insight on geopolitical affairs, politics, and everything in between...I'm all for individuals becoming well educated citizens of the world.
Enjoy freshman year...it's a doozy.
