A Dog's Purpose

A Dog's Purpose is a 2010 novel written by American humorist W. Bruce Cameron, author of 8 Simple Rules for Dating my Teenage Daughter and How to Remodel a Man. 

The book chronicles a dog's journey through several lives via reincarnation and how he looks for his purpose through each of his lives.

The novel stayed a New York Times bestseller for forty-nine weeks,garnering critical praise from such sources as Temple Grandin, famous for her study of cattle behavior; Kirkus Reviews; and Marty Becker, resident veterinarian on the early-morning television show, Good Morning America. A sequel followed in May 2012, titled A Dog's Journey, following the same dog after the events of the previous book. The film rights of the book were bought by DreamWorks. A film of the same name was released in January 2017.

The narrator first starts out as a feral puppy. A few weeks later, after being nursed by their mother, a feral as well, the dog and his siblings Fast, Sister, and Hungry go outside of their den to explore the woods around them. Soon after, men come and capture them. The dogs arrive at a place called the Yard, where dozens of abandoned dogs reside under the guidance of a gentle old woman whom the narrator calls Señora. The narrator, who is soon named Toby by Señora, adjusts to his new lifestyle. One day, many of the newer dogs at the Yard are whisked off to a building (a veterinarian office). 

A new dog arrives, named Spike, who is very aggressive towards the other dogs. When Spike attacks Sister, Toby joins in and Spike bites his front leg. Not long after, animal control agents arrive with orders to shut down the place due to poor sanitation and welfare conditions. Many dogs, including Toby, are subsequently euthanized.

Toby is reincarnated as a Golden Retriever and is nursing from a new mother. A few weeks after birth, when Toby and his new brothers and sisters have matured enough, he and the others are allowed to play outside the cage. Toby climbs up onto a table and bites the doorknob, opening the gate to the outside world and leaving him to explore the real world. A truck driver picks up Toby on the road and calls him "Fella." The man drives to a bar. After the man has been gone for several hours, Toby begins suffering from heat exhaustion in the cab.

However, a woman appears and breaks the car window. She revives Toby with water from a water bottle. The woman brings him to her car and returns home. The woman introduces Toby, renamed Bailey, to her son, Ethan, who is overjoyed to have a puppy of his own. Over the summer, Bailey enjoys himself, playing with Ethan every day. Bailey becomes accustomed to Ethan's school routine and the summer tradition of going to the Farm, where Ethan's grandparents live.

Over the course of many years, Bailey lives a full life with Ethan. He accompanies Ethan through many difficulties, including arson, causing a permanently injured leg, ending Ethan's athletic career. Ethan goes to live with his grandparents at their farm in Michigan so he can be with his girlfriend Hannah and to finish his senior year in high school. Around that time, things are not going well in the family, with Ethan's injury, an eventual break up with Hannah, and a divorce between Ethan's parents. Soon after moving, Ethan goes off to college, leaving Bailey with infrequent visits from him during the holidays. Bailey's health starts to decline, with him taking naps very often and being weak. Soon, Ethan's mother and grandparents take him to the vet, where he is once again put down.

Bailey wakes up once again as a German shepherd. Bailey, who realizes that he is now a girl, is picked out and named Ellie by a police officer, named Jakob, and trained to be a search-and-rescue dog. After Jakob is wounded, Ellie is transferred to one of his colleagues, Maya. Ellie learns to work with Maya. Eventually, Ellie dies once again, sure that she has finally fulfilled her purpose.

Much to her surprise, however, Ellie is born again, this time as a male Labrador retriever. Wendi, his new owner, is ecstatic with her new pet (whom she names Bear), but she is unable to keep him because of a no-pet rule in her apartment building. Instead, she gives him to her mother, who is dating an alcoholic. The mother's boyfriend, fed up with the dog upon receiving a notice that he needs to provide better living conditions, ditches him on a country road. Bear recognizes his surroundings, having been there before with Ethan. Using the skills he learned as Ellie, Bear is able to trail the scent of one of the farm's animals to the Farm, where Ethan lives. Ethan, now an elderly man, decides to keep Bear, renamed Buddy, and marries Hannah.

From Wikipedia