"The Call of the Wild" by Jack London

Large, strong and smart, Bucktoughens to his new life. But even the toughest dog can be worn down byconstant work, and after 3,000 miles of pulling sleds, Buck nears theend of his rope.
Cast away as no longer useful, Buck is acquiredby greenhorns whose inexperience nearly kills him, but after being savedby John Thornton, he at last finds a man he can love.
Then on aremote gold-hunting expedition, Buck hears a call emanating from thewoods and speaking to the wild heart of his distant ancestors. The lureof it almost balances the great love he bears for Thornton, but eventstake him away from his old life... and into legend.
Please be aware this book contains graphic descriptions of violence and animal cruelty.