The Call of the Wild by Jack London

Buck, a Saint Bernard-Shepherd dog, lives a comfortable life in the Santa Clara Valley with his owner, Judge Miller. One day, Manuel, the Judge's gardener's assistant, steals Buck and sells him in order to pay a gambling debt. Buck is then shipped to the "man in the red sweater" to be broken. Then Buck is shipped to Alaska and sold to a pair of French Canadians named François and Perrault (for $300), who were impressed with his physique. They train him as a sled dog, and he quickly learns how to survive the cold winter nights and the pack society by observing his teammates. He and the vicious, quarrelsome lead dog, Spitz, develop a rivalry. Buck eventually bests Spitz in a major fight, and after Spitz is defeated, the other dogs close in, killing him. Buck then becomes the leader of the team.