Obviously, this is not quite the "author literature" but it is a perfectly calibrated product for 7-8 years, boys and girls. The two heroes are very timely brother and sister, and their characters are well marked. The identification machine casts a wide net. The run effect is exploited to the maximum, with child portrait repeated every time, the same excuse-red thread that runs on multiple volumes and constant reminders to read the other volumes. Adventure, certainly, but the adventure very predictable, very structured - that never forgets the cash drawer.
But no matter, the children love and that is what is instructive.
A word about the translation: it is exemplary. Marie-Hélène Delval perfectly gives life to these two children, and his descriptions are poetic accents.
In short, if you know of children 7 years old, do not hesitate to make them that little gift. If necessary, "prime the pump" by reading with them the first book, and you will have peace ... for 26 volumes.