Premise: Comet in Moominland (Swedish: "Kometjakten" / "Mumintrollet på kometjakt" / "Kometen kommer") is the second in Tove Jansson's series of Moomin books. Published in 1946, it marks the first appearance of several main characters, like Snufkin and the Snork Maiden.
Hypothesis: Tove Jansson's first Moomin book was published before 1946.