Kasie West is always a safe bet for a cute, fun story. For some reason this is one of her better ones in a while. I think a big part of it is that Norah is easily likable (despite her odd perception that her thoughts are weird or off-putting which didn't actually seem to be the case at all). Plus, even though some of her reactions are off base they're understandably justified from assumptions of a seventeen-year-old girl. So they're not annoying. And they don't wreak havoc with the story. Willow is also fun and very likable, really all the characters are. They move the story forward through a light plot by having a good time, even when they're fighting.
As is often the case, it ends too abruptly. It wraps everything up nicely but too quickly in barely a few summarizing pages when the fun of the book was the dialog and character interactions.