The most helpful guide that I have found here is frogbeastegg's "Beginner's Guide to Medieval Total War". It is topped in the MTW Guides forum. It does not assume too much knowledge about the game beyond the contents of the manual and it is very enjoyable to read. However, it is certainly not required reading and, if you would prefer to explore a game on your own, it is comprehensive enough to spoil that part of the fun. On the other hand, I doubt that Medieval Total War is the kind of game that loses its attraction once you learn how it works, so I would have a look at it.

Verrucosus