"Lord of the Flies" by William Golding.

The novel is about the adventures of a group of English children left alone (or marooned) on a tropical island. They degenerate into savages, due to lack of adult supervision. 

The boys have been evacuated from a war zone and dropped by plane. They choose 12-year-old Ralph as their leader. Of course, there are much younger boys in the group. Things go well for some time. Then troubles start. 

One day, the boys are making a fire on the mountain so that any ship coming near the island will notice and rescue them. The fire spreads beyond their power and kills one of them.

The boys kill pigs on the island for food. Sometimes they see beasts (real or imagined). The younger boys (or "littluns") once talk about a beast from water and the "biguns" allay their fears. Then, a dead airman dropped by parachute to the island is mistaken for a beast with wings. 

Later, Jack Merridew becomes rebellious against Ralph and the group splits into factions. Ralph's factions contains Ralph, Piggy, Sam and Eric. The other boys support Jack. 

One day, Jack's group attack by night and take Piggy's eyeglasses. Piggy has to be led. When Ralph's group go in search of the specs and leave Piggy behind,he is killed by Jack's group. Simon (in Jack's faction) has earlier died. Ralph escapes but the twins (Sam and Eric) are captured. 

Ralph is now alone,feels lonely and makes attempt to reconcile with the others. Jack's group hunt Ralph the following day and Jack dies in the battle. 

Just then, a naval officer comes with a ship to rescue them. All the boys weep over the deaths of their 4 colleagues - the burnt boy, Simon, Piggy and Jack.