Knowing all original comics and having watched "The adventures of Spirou and Fantasio", "Gaston Lagaffe" and this one in a row, this one is way better:
All 3 movies from the Franquin/Spirou-universe have in common, that they include a lot of details of all kinds from the comics and don't depend on a heavily modified CGI look like "The Adventures of Tintin" (2011; which, honestly, was pretty good in many ways), or CGi/SFX for the action part, but still provide a colorful look and believable depiction of inventions from the comic books.
This one is a movie for fans of the comics AND for children, as they have been made in earlier times, like the War of the Buttons in 1962, or stories from "Le petit Nicolas", the legendary french childrens book.
While in the first half, the movie struggles a bit while introducing the "universe", characters and their relationships, it slides into the storyline, action, adventure and suspense in the second half.
The story doesn't rely on being set to a certain decade and may well be the 60ies or the presence (well, apart from mum's car). It tells a story of kids, their everyday life, school, friendship, worries, feuds, and how they interact with all kinds of adults, in a world, that hasn't grown over-complicated, yet.
Last, not least: The actors are well chosen and Pierre Richard shines anyway.
