It's Season Two of K-On!!. They celebrated with a second exclamation mark. It's basically the same as last time, but with even less plot. You could watch most of the episodes out of order and never know, despite the slow build-up to the girls' graduation. Come to think of it, a few of these episodes are out of order. Ep.24 ("Graduation Ceremony!") is the final episode, after which eps.25-27 are bonus episodes set earlier in the series.
Ep.25 ("Planning Discussion!") - after episode 21
Ep.26 ("Visit!") - before episode 23
Ep.27 OVA ("Plan!") - before episode 14
You can see how this show kicked off the anime industry's "cute girls adorably doing nothing" moe boom. It's lovely, but it's also less memorable than Season 1 and it's more often spinning its wheels. Kyoto Animation was doing sequel seasons for both this and Haruhi Suzumiya at the same time, which in the eyes of some fans has been blamed for a second-season decline in quality in both shows. (You can't blame K-On!! for the Endless Eight, though. That happened because the Haruhi Suzumiya production team had a gap to fill when one of their planned storylines got used for the movie.)
The show's still about five girls who like hanging out together, drinking tea, eating cake and occasionally rehearsing for their school club band. They're not particularly good musicians, but they have great chemistry (both as friends and as performers) and on a good day they can rock a stage pretty well. (Caveat: don't let Yui near the microphone. See ep.20. Who gave that girl licence to burble on about whatever entered her worryingly random mind?) If you're interested in music, you might like this show. However even if you're not interested in music at all, you might still like the show anyway. It's not a music-heavy show. No one's intense about anything. The girls' priorities are:
YUI THE LOON: food, sleep, anything that enters her brain. Yui's a lovely, happy, optimistic girl, but also the kind of space case who's quite likely to do something unpredictable when trying to do anything. You'd worry about her going shopping on her own. You'd worry about her putting her shoes on. She's just about realistic enough not to break the show's credibility, but in real life you'd have zero expectations of her chances at university.
RITSU: having fun, doing things at top speed, play-wrestling. We learn that last one in ep.18, which is the first half of a two-parter in which everyone votes on who's going to be in the class play. Terminally shy, ladylike Mio is nominated as Romeo, while Ritsu of all people is shotgunned into playing Juliet. There were some comedians among the voters, I see. That was a particularly amusing pair of episodes.
MIO: not being noticed, not being embarrassed, getting her friends to be a bit more serious. So doomed.
AZUSA: a lot like Mio, while also trying to resist the gravitional pull of her friends' free-associating slacker attitudes. She wants to stay her old serious self. Also doomed.
MUGI: goodness knows. Working out what's going on in Mugi's head can be even harder than trying to read Yui.
Individually, there's some good sense in these girls. As a gestalt, they obey the Principle of Maximised Goofiness. There's nothing essential about this series and it would be hard to argue with anyone calling it disposable... but it was both successful and influential and I watched it all happily. Natsuki enjoyed it too. It could entertain anyone, from three years old to a hundred and three. Apart from anything else, the animation is fantastically subtle. All the girls are liable to be saying more in their body language than in their dialogue (funny and sparky though that is too). There's unlikely to be anything dramatic or deep happening, but it's still closely observed and you can still watch the characters as actors in more detail than in almost any non-theatrical anime. Admittedly that's a Kyoto Animation trademark, but K-On!! is probably their most striking example of that, since there's such a gulf between its fluffy, apparently empty-headed text and its deceptively rich non-verbal content.
It's a happy show. It made me laugh. At its best, it's brilliant. At other times, the episodes blend into each other a bit. However its comic timing can be to die for and the girls' friendship is so palpable that it's almost another character. Everyone getting into death metal in ep.10 is simply adorable, for instance. It's both throwaway and really impressive. I'm looking forward to watching the movie tomorrow morning.