Guest books are for museums, funerals, places like that. Friendship is less formal, I believe. But I didn't bring anything to eat. Are you supposed to bring snacks to a party you weren't invited to but are attending anyway?

[ It's not as if he'll run out and buy snacks or anything, but this question is probably more than half genuine. Because you could count the number of parties Tsurubami has been to on one hand, and that was just a bonus page. ]