Ernest Hemingway's first novel, "The Sun Also Rises," treats of certain of those younger Americans concerning whom Gertrude Stein has remarked: "You are all a lost generation." This is the novel for which a keen appetite was stimulated by Mr. Hemingway's exciting volume of short stories. "In Our Time." The clear objectivity and the sustained intensity of the stories , and their concentration upon action in the present moment, seemed to point to a failure to project a novel in terms of the same method, yet a resort to any other method would have let down the reader's expectations. It is a relief to find that "The Sun Also Rises" maintains the same heightened, intimate tangibility as the shorter narratives and does it in the same kind of weighted, quickening prose.