A gaggle of high school girls sitting around eating cake and drinking tea sounds like the world's most unbearably dull thing ever, and it probably is, but going through the motions of daily life isn't half bad, but just watching it is pointless none the less to those who want more. STORY: ...I'm honestly at a loss here, how does one grade a story, when there isn't a story at all. K-ON! is just that, no story, no conflict, no evil organizations to defeat, no romance, nothing. I challenge anyone to think of a better phrase to describe K-ON! than, "Pure sweet pointlessness." Ending the reviewright there would be easy, because I described accurately enough, but my joking(?) aside... Umm, actually I'm not joking, K-ON! is pointless to the point of having no point of even existing, I mean there's more than enough daily lifes of who-ever-the-hell to satisfy all life slicers, so why does K-ON! get the most attention? There's some fan pondering once in a while (Yet there's several vacation swimsuit arcs), but less so than (Or more than) Lucky Star, so why K-ON!?
That is where I got an answer: It's simplicity and unpretentious nature is what captivates those who just want to sit and watch something, the way you just want to admire the sunset or something along those lines. K-ON! is the quintessential series to check out in that regard, it doesn't get full of itself, it doesn't bombard you with plot twists or heavy explainations, it's pure enjoyment for those who enjoy watching people just hanging out and do whatever.

That in it's self is the problem with K-ON!, it's nothing, literally. There's nothing it does to grab ahold of your attention, or give a sense of urgency. No plot details to explain other than Yui Hirasawa is looking to join a high school club, of course a series as itself has no need to, as it is meeting a status quo for those enjoy this kind of manga, but there are many who will be turned away for that reason and more. K-ON! is also incredibly sweet and soft on attitude as well, the characters are as followed: Yui Hirasawa the bubbly clumsy guitar player, Ritsu Tainaka the tom boy drummer, Mio Akiyama the mature yet very femine bassist, and Tsumugi Kotobuki the kind rich girl (Literally, she's what I'd like to call an unreallistic not character as her character trait is nothing more than being a wealthy person).
And along the way, another band member joins up, an underclassman Azusa Nakano who goes through what most first time readers of K-ON! go through, discovers the club by their performance (The reader discovers K-ON! through sheer popularity), only to find out they laze about doing nothing (The reader finds out how nothing actually goes on), and gradually goes with the flow of things (Reader excepts its, and just reads for the sake of reading). These characters are not multi faceted people, and are questionably single dimensional (Though towards the later parts, there's a touching moment where the others cheer up a sadden Azusa who reallizes she'll be alone when her friends move on and graduate from high school), but they serve the status quo, they are about as ordinary as slice of life characters can get, nothing more nothing less.

And you know what? That is okay. It's okay to read something without any purpose, it doesn't fail at being entertainment, a specific type of entertainment despite it's popularity, but entertainment none the less. But if you want substance, and not something as soft as a marshmallow, K-ON! just doesn't appeal to that in any way. You're basically looking in the coloring book section for Sigmund Freud in a sense.

ART: Not too detailed, but not poor either. It accomplishes what it sets out to do well, displaying cute girls doing cute stuff. The artwork is just as uninsulting as the subject material, and it is paired with it's simple nature with a simple style: 4 Koma (Panel).

OVERALL:
The Mixed:
+/- Pure and sweet in nature, it doesn't insult or aggravate in any way. / There is no substance, those looking for deep meanings, fasicnating characters and a story for the ages, then you're literally wasting both yours and the manga's time.

Maybe being overrated isn't a bad thing as long as you are doing your genres a good job. The series is having a weird choice though, K-ON! colledge years, where the girls drink tea and eat sweets for their semesters. If finding high schoolers adorable was already a farfetched idea, then finding colledge girls acting like preschoolers adorable is just simply perposterous.