Let me start by saying I've never read the book. Math Teacher tried several times but simply couldn't finish the book. So we both had no comparison.
The book started with the monster being born, the movie ended with the monster being born. So they were of different timelines. The movie was told from the perspective of Igor the Assistant, with the backstory of the mad scientist Victor Frankenstein.
It was an ok movie with Daniel Radcliffe (of Harry Potter), James McAvoy (of Professor Charles Xavier in X-Men), and Andrew Scott (of Moriarty in Sherlock). Andrew Scott still reminded me of Moriarty in Sherlock. Daniel Radcliffe was a bit stiff in his acting skills. But, James McAvoy stole the show. He was a completely different character. Insane but with a touch of humanity.