I'm a troll for Examkrackers so there is a little bias. I never saw or even heard about Nova up until now, but I doubt any prep company can beat Examkrackers. You'll get all you need in their books. I fell in love with those books and enjoyed my experience working with them. It'll get you real comfortable with ALL the sciences. Some people wouldn't trust them because it is so concise. However, there were a few required equations in Physics which they said weren't needed (just memorize them). Other than that, they covered everything I needed. I did very well on both science sections using almost entirely EK material. Go for it!