What is the book "The Sun Also Rises" about?

Context: The Sun Also Rises is a 1926 novel by American writer Ernest Hemingway, his first, that portrays American and British expatriates who travel from Paris to the Festival of San Fermín in Pamplona to watch the running of the bulls and the bullfights. An early modernist novel, it received mixed reviews upon publication. Hemingway biographer Jeffrey Meyers writes that it is now "recognized as Hemingway's greatest work" and Hemingway scholar Linda Wagner-Martin calls it his most important novel. The novel was published in the United States in October 1926 by Scribner's. A year later, Jonathan Cape published the novel in London under the title Fiesta. It remains in print.

The novel is a roman à clef: the characters are based on people in Hemingway's circle and the action is based on events, particularly Hemingway's life in Paris in the 1920s and a trip to Spain in 1925 for the Pamplona festival and fishing in the Pyrenees. Hemingway presents his notion that the "Lost Generation"—considered to have been decadent, dissolute and irretrievably damaged by World War I—was in fact resilient and strong. Hemingway investigates the themes of love and death, the revivifying power of nature and the concept of masculinity. His spare writing style, combined with his restrained use of description to convey characterizations and action, demonstrates his "Iceberg Theory" of writing.

Answer: The Sun Also Rises is a book based on people Hemingway knew from his life in Paris, fishing in the Pyrenees, and a trip to the Pamplona festival in Spain.