I. Introduction
A. Introduction to the author: Ernest Hemingway.
Ernest Hemingway was born in Oak Park, near Chicago, on July 21, 1899. He had been a reporter for the Kansas City Star, and then volunteered to serve as a driver on the Italian front. After the war, he worked for Toronto Star as a foreign correspondent, and then returned to Paris.
His first book, Three Stories and Ten Poems, appeared in 1923. With the publication of The Sun Also Rises in 1926, Hemingway became the spokesman for what Gertrude Stein had called “a lost generation." Hemingway's stature as a writer was confirmed with the publication of A Farewell to Arms in 1929. Later he published Death in the Afternoon in 1932, The Green Hills of Africain 1935, To Have and Have not in 1937, The Fifth Column in 1940, and For Whom the Bell Tolls in 1940. In 1954 he was awarded a Nobel Prize for his "mastery of the art of modern narration," which showed in The Old Man and the Sea written in 1952. He became a public figure whose pronouncements and adventures were publicized throughout the world. In 1950, he publishedAcross the River and into the Trees. In the early morning of July 2, 1961, standing beside his beloved gun rack in his home, he died of his favorite shot-gun, in his own hand.
Brief introduction to A Farewell to Arms
Lieutenant Frederic Henry was a young American attached to an Italian ambulance unit on the Italian front. He was introduced to British nurse Catherine Barkely by his friend, Lieutenant Rinaldi.
Between ambulance trips to evacuation posts at the front, Henry called on Miss Barkley. He liked the frank young English girl in a casual sort of way, but he was not in love with her. Before he left for the front to stand by for an attack, she gave him a st. Anthony medal.
At the front , Henry ，badly wounded in the legs, was taken to a field hospital, later he was moved to a hospital in Milan. Catherine Barkley came to the hospital and Henry knew that he was in love with her. A doctor told Henry that the operation on the knee could be performed the next day. Meanwhile, Catherine managed to be with Henry constantly.
After his operation, Henry convalesced in Milan with Catherine Barkley as his attendant. Together they dined in out of the way restaurants, and together they role about the countryside in a carriage. Catherine often came to Henry's hospital room at night.
Henry's wound had healed in autumn, but the head nurse accused him of bringing on the jaundice by drinking in order not to being sent back to the front, so his holiday was cancelled. Before he left for the front, he knew Catherine was pregnant. Henry returned to the front with orders to load ambulances with hospital’s equipment and retreat to the Povalley, finally they gave up their cars and struck out on foot forUdine. Within sight of Udine, one of Henry's group was killed by an Italian sniper. The others hid in a barn until it seemed safe to circle around Udineand join the main stream of the retreat toward theTagliamentoRiver, Henry was detained on the bridge, but in the dark of night he broke free, plunged into the river, and escaped on a log. He crossed the Venetian plain on foot. Then jumped aboard a freight train and rode to Milan, where he went to the hospital in which he had been a patient. There he learned that the English nurses had gone to Stresa.
During the retreat from Caporetto Henry had made his farewell to arms. He met Catherine in Stresa and escaped to Switzerland by the help of a bartender in order to avoid authorities came to arrest him for desertion. During the rest of the fall and the winter the couple spent a wonderful and unforgettable time together in Switzerland.

"...he (was) a reporter for the Kansas City Star (before volunteering) to..."
use simple tense when you can.

"...foreign correspondent (before he went) to Paris."
you never mentioned he was in Paris. how can he "return" to Paris?
also the same problem as above. if you use "and then", you need to tell the reader when is "then". like "he worked here for how long, and then he did that", or "he worked here, and then he did that in what year".

"His first book, (")Three Stories and Ten Poems("), appeared (on shelves) in 1923."
need to say appeared where, or just use "published".
also you need to do something to let the reader know you are talking about a book title. i faintly remember it being quotation marks for books. might be underline.

awarded a Nobel Prize for his "mastery of the art of modern narration," (as shown) in

"Henery...hospital, (and) later he was moved..."

"...managed to (stay with) Henry."

as an advice the summary is way too long. not brief at all. tell the reader what kind of story it is and the major events, not how everything happened.