I agree with the critical lens which states "The best literature may entertain readers or disturb them, but above all, it must make them think". This statement means that the most important thing a book can do is to make the readers think about what he/she reads. It doesn't matter if the story is enjoyable or upsetting, if it achieves this goal. This is true in the two pieces of literature.
In Death of a Salesman, you start thinking about the story, when he gets the flashbacks, and he knows, that he did something wrong in his life. But he doesn't seem like he want to change it. He thinks you need to be well liked, to succeed in your life. But that is wrong.
You don't need to be well liked to succeed, it's more about what and how you do it, and that is it, what that book makes you thing about. Willy is too much in his own world. When he became the salesman, he thought, that it would me easy to make sales, just over the phone, like the one Salesman did, that impressed him to become a salesman.
Even when Biff grow up, Willy tried to make him a successful man. He was popular and well liked, but he was a little bit to dumb and failed math in his senior year, so he couldn't go to college. That's what hold him back from becoming a successful man.
When you read through the part, where you hear, that Biff failed math, and Willy is cheating on his wife, you think about, that Willy won't be happy in his life again, because he his too old and still thinks, he is the New England man, he thinks he is well liked. This makes most of the depressing mood. The whole book is really depressing and sad. It makes you think, that you don't want to end like that in your life. It makes you think about, how somebody misunderstands "the American Dream" and it prevents you from making the same mistake. It ended, when he killed himself to give the money from the insurance company to his son to become a better person. And that the worst moment in the whole book.