What is a queston you can ask yourself when reading so that you can understand the tone?

Look at the passages where the author describes the isolation and insanity that dr frankenstein has

The answer is "he was bad enough in all conscience, but the devil himself could not temp him to turn slave-trader. satirical is a synonym for sarcastic. so when the author says that tom walker could not be tempted by the devil he does not literally mean "the devil" but he means that he is too morally upright to become a slave-trader.