Theodore Boone, Kid Lawyer. It's a strange title. I mean, if I were a kid, I'd rather pick up a book titled "Theodore Boone" or even "Theodore Boone [insert title of case here]."
It is obvious from the writing that this is Grisham's first novel for children. He states things it might be better to just hint at. For example, that Theo's best friend April is a girl but just a friend. Instead, Grisham could have established this through the dialogue and interactions Theo and April have. Not to mention that April appears only briefly, as if Grisham is trying to introduce her now so her appearance in another novel is less strange. There's also a reliance on going through the motions of each day, outlining where Theo had dinner, etc. when these snippets have no seeming relevance to the narrative and only seek to slow it down.
I haven't read any of Grisham's adult novels, so I'm not sure if he's writing down to children, or if this is simply how he writes. The novel is not all bad. Grisham clearly outlines court procedures and explains the judicial system as he goes along, giving the reader applicable knowledge as he goes along. Because of this, I could see the book being used in middle school classrooms as a supplement for social studies classes. However, unless I come across a serious, government and civics focused twelve year old, I can't see this book leaving the shelf.