If you're reading this, you probably know what the Redwall Abbey books are, and it's likelyyou've read them. If not, I direct you to the official website, Redwall.org, and shortly thereafter to a library. Regardless of whether you want to play Heroic Tails, you should begiving the books a try.
Now, assuming you understand Redwall, you're halfway there. All that's left is to describe the RPG side of things, and you should be moving along quite nicely.