Comet's Tale by Steven Wolf

Comet's Tale is a story about a friendship between two former winners, both a little down on their luck, who together stage a remarkable comeback. A former hard-driving attorney, Steven Wolf has reluctantly left his job and family and moved to Arizona for its warm winter climate. There he is drawn to a local group that rescues abused racing greyhounds. Although he can barely take care of himself because of a spinal condition, Wolf adopts Comet, an elegant cinnamon-striped racer. Or does Comet adopt Wolf?  

In Comet's Tale we follow their funny and moving journey as Wolf teaches Comet to be a service dog. With her boundless enthusiasm and regal manners, Comet attracts new friends to Wolf's isolated world. And finally, she plays a crucial role in restoring his health, saving his marriage, and broadening his definition of success.