Finally decided to look werewolves up on Wikipedia to try and find a better explanation of the game than I can (or have the energy to type out!) give. Here's the link - the game was originally based on Mafia members as the bad guys, but it has the werewolf variation details as well.
On that topic - the two further games I've signed up for have 20+ players in each of them. The two games I've played in so far have only had 9 in each, so have been over in a couple of days. L's just been playing in a Narnia game with 20+ players and one thing has become painfully obvious - I am going to have to be much more organised and paying attention if I want to actually correctly guess a wolf!!! The Narnia game lasted a week, and could have gone on longer if the village hadn't played quite so badly and failed to lynch ANY of the max evils!!! Tee hee!!