Comet in Moominland by Tove Jansson

To mark the 80th anniversary of the Moomins, a quick and gentle read for hot summer days which is also a parable for living under the threat of total nuclear annihilation.

A comet is speeding towards Earth - will it destroy everything and everyone? Moomintroll decides to investigate. So, with Sniff, he sets off on an expedition to ask the Professor about the comet. On their way they meet Snufkin and the Hemulen who rescues them from a secret underground tunnel - but can they escape the dangerous crocodiles that lurk. . .

They seem to grow in wisdom and delight every time I read them - Philip Pullman