In the case of "Man of Steel", there was VERY little extra added to the actual novelization (I know, I read it multiple times after seeing the movie in theaters twice). If the novelization here is any indication, there was nothing important or relevant left out. There was only ONE major change that I saw from one on-screen scene versus the book. In the scene with the interview, Lois and Kal-El/Clark are not interrupted and thus have a bit more back and forth than the movie actually showed. It (the scene in the movie) took away the "humor" of the scene in favor of smoothness between moments.

CLARK: No. I'm just worried I'm a jinx.
JONATHAN: A jinx?
CLARK: Yeah. Let's face it, ever since she's known me, Lois's been kidnapped, frozen, pushed off buildings, almost stabbed, poisoned, buried alive and who knows what else, and it's all because of me.
-"Contact" (You're not her jinx, you're her blessing.)