How did Ernest Hemingway's books effect life in the 1930s?
Well, it is an interesting question and I am guessing that you are asking how his writing may have "affected" life in the 30's rather than "effected it."
I can't say that I would put much stock in the idea of someone's writing, even someone as widely acclaimed as Hemingway, actually having a large effect on the society or the lifestyle, politics, etc., of the times. In his case, Hemingway wrote about things that other people had been hesitant to, but a great deal of his fame and notice came after his death.
Some might argue that his willingness to address some of the troubling aspects of society in the United States after WWI was important in bringing some of those issues to light. He also wrote about his experience in the war in a way that questioned motivations and even some of the actions of individuals and armies alike. This was a common reaction in the art and literature of the time as all over Europe people reacted to the devastation and senseless death with a willingness to question the glory and honor of warfare that was previously celebrated endlessly in much of literature and art.
His influence as a constantly studied and revered part of American literature is likely far more important and long lasting than any real effect he had on life in the 30's.
Building on the idea of reflecting as opposed to impacting, I think that the Hemingway hero was one who was able to deal with the stressful conditions placed upon him and display a sense of "grace under pressure." The regular person, what Clive James would call "the shy guy," is one who was besieged with so much in terms of stressful and difficult conditions. The average person in the 1930s dealt with economic uncertainty in the form of a crippling economic depression. They also faced political uncertainty, as traditionalist political orders were challenged by charismatic leaders who sought to mold nations in their own images. The Hemingway hero's code of displaying grace under pressure is a reflection of how life was to be lived in this difficult and challenging time.