This book reminded me of those forgettable Martin Short family-friendly movies from the 1990s like The Fairy Godmother, in which a one-(not-so-funny)-joke premise becomes the basis for the entire movie. Here, the supposed joke is that one of those timeless detective kids from the books of our youth has to face a world in which everyone ages, everyone grows up, and no one solves a crime with a magnifying glass.
I must say that I do not like this style of writing in which every paragraph ends with something cutesy, nor did I appreciate the thought of an attempted suicide being played for laughs.
I hate to sound like a hater, but this whole thing was a soft little cream puff, and like a cream puff there was nothing solid at its core. If you are looking for playtime, here it is. If you are looking for a substantial novel written by a master wordsmith, look elsewhere.