Little Brother by Cory Doctorow
The Marcus Yallow books are fun and sad. Fun because kids fight for justice using scant resources and their wits. And Sad because Doctorow never really gives "the bad guys" a chance to explain why they do what they do.
Homeland by Cory Doctorow
Perhaps as Marcus gets older, the complexity of the books will increase. For now, I find myself just reading them and waiting....