This is a short story from 1965, reproduced lovingly.
Instead of the traditional cartoon cells, 50-100 words are illustrated on a double page by a beautiful coloured pencil drawing. You can see the entire Gaulish village (or much of it) on one double-page spread, as a young Asterix and Obelix go to the Druid's cauldron.
It is a short story, and therefore there are not as many pages as in the regular books. However, where else can you see our heroes as children? Because of the scale of the drawings, children can then imagine other adventures that Asterix and Obelix might have had as children - the story needn't stop at the end.
And it might provide inspiration or hope for young readers who are not that strong, or who are being bullied, that they might grow up into a hero.
Overall, because this is such a different book, I would not get this book until you have read (say) at least half the series, and then, with the characters firmly established in your mind, you can then appreciate all of the subtleties in the drawings.