I've never read Watership Down, which makes me sad because I really want to! I am, however, a huuuuge fan of Redwall. Warriors as well, though not as much due to the less-elegant writing.
BUT
LET ME TELL YOU ABOUT MRS. FRISBY AND THE RATS OF NIMH
You know the move "The Seret of NIMH"? That was based on a book. Now, I had the misfortune of reading the book before seeing the Don Bluth movie, which completely ruins the glory of the book. Seriously, though, it's my absolute favorite talking animal book and if you haven't read it, you should give it a try!