Jack London 
Call of the Wild [PDF ebook] 

Buck is a big dog living a comfortable life in California. When gold is discovered in Canada, he is stolen from his home, taken up to the Klondike region, and forced to pull dog sleds. As time passes, Buck discovers the instincts of his ancestors and learns how to survive in the wild, endure freezing conditions, and deal with cruel men and dogs. Finally, Buck finds a kind master, but in the end, the call of the wild may be too strong. This is an unabridged version of Jack London’s classic American survival story, first published in 1903.