1) The book is called Call of the Wild by Jack London and tells the story of a dog named Buck.
2) Buck starts as a domestic dog in California but is stolen and sold as a sled dog in the Yukon during the 1897 Gold Rush. He must learn to survive cruel conditions.
3) Over time, Buck's instincts return and he becomes a leader, helping to defend his new master Thornton, but Thornton is killed and Buck rejoins a wolf pack, fully wild once more.