Enslaved by Ducks was a great book. It wasn't fiction, but was actually a funny account of a man who started with one animal and just kept getting more and more! (Just like many of us here on BYC!)
There is a book called the "Firebringer" about deer that I read this past summer and it was excellent. That same author also writes another book about wolves, but I can't for the life of me remember what it's called.
Also, there is another series called "The Firebringer" and it is about a group of unicorns. This is more of a younger series, but I'm almost 20 and I still enjoy books like that every now and again I believe there were four or five books in that series.
There are a few other animal books I know of, but just can't remember. I'll have to go through my collection since I'm home for the weekend and I'll get back to you.