Their MobileMe service
was down over the weekend as well for many people. Seems like their transition to iCloud has been a bit rocky.
Not sure how it would easily affect iBooks the same way though.
AppleTV doesn't store anything-it is all streaming, so it has to go to Apple's servers to get movies and TV shows.
iBooks are on your iPad/iPhone. You don't need a connection to read them. It would affect buying them, of course.