Characters in a book can't be run of the mill. They need to be interesting, so that your readers will want to hang out with them for the course of the book. No one wants to be exiled to yawnsville when they start reading.
So, how do you make your characters interesting? It's all in the details.
For instance, I recently finished a Middle Grade, but it was based on a story I'd written when I first started writing. The MC is forced to visit his grandfather who lives in a small town. This is the scene where he meets up with a couple kids down the street. The original reads like this: