A Kind of Paradise, by Amy Rebecca Tan

Straight-A student Jamie has messed up badly.  Blinded by her desire to impress a boy that she has a crush on, she's been caught violating her school's Honor Code. As a consequence, she has to spend the summer doing community service. There will be no camp and no vacation trips.  Instead, she has to work at her town's public library.

But to her surprise, Jamie quickly discovers that the library is full of lots of fun people (both staff and patrons) and that the work is actually pretty interesting as well.  Moreover, the people have lessons to impart, helping Jamie see where she went wrong and develop her interpersonal skills along the way.  In return, Jamie helps an effort to save the library from closure.

Half a love letter to public libraries and the other half a personal development story, there's lots going on here.  Given the target audience, very little of it is subtle. The ending is all a bit too rosy for me as just about everything works out.  I didn't find the dialogue very realistic, but the characters are quirky, charming, and memorable.