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.
The second Moonmin book by Tove Jansson had Snufkin and the Snork Maiden in it and was titled "Kometen kommer"
The book I listed was actually the third book in the series.  It probably didn't recognize that in the context.