All the books in the series are great, but I think the first is the best. While reading this, I got to learn how Encyclopedia's career as a boy detective got started. He solves his first big case at the dinner table and his father gets a new respect for his son. I learned how he got his partner, and how they met. I understand his first problems, and I understand how much he's progressed throughout the series. I also learn how he got his enemies, and what lengths they would go to to make him disappear.
-AbdurRahman