Although you are a "novice" to philosophy, you might still be interested in The Critique of Pure Reason by Kant. It is notoriously difficult, but majoring in philosophy doesn't make it easier anyway, so it's worth it just to jump in and fight your way through. It is hard, but rewarding, and will set you up well for the Groundwork of the Metaphysics of Morals which you may have been introduced to in your ethics course. For a scientific, logical mind, Kant is a good philosopher. I think he himself discovered some things in physics, though I don't recall what exactly. Kierkegaard is a little less heavy on the rationality stuff in comparison to Kant. Either/Or is a fascinating comparison of the aesthetic life and the married life; you could try an abridged version, because it is two volumes long. I highly recommend Kant though.