I also love Barbara Kingsolver, as many have mentioned, and her "Animal, Vegetable, Miracle" is a book I think anyone on BYC would like.
I loved "To Kill a Mockingbird" and in fact have a 15 year old cat named Scout.
Laurie R. King's "Mary Russell" series of books, starting with "The Beekeeper's Apprentice" are excellent.
My favorite author is Robin McKinley, one of hers you might enjoy (featuring dogs) is "Deerskin."
Farley Mowat is best known for "Never Cry Wolf," but my favorite books of his are "The Dog Who Wouldn't Be" and "Owls in the Family." You laugh until you cry (or wet your pants) when you read those.