Tove Jansson met the printmaker Tuulikki “Tooti” Pietilä at a 1955 Christmas party in Helsinki, and the two shared a turntable, then the next 45 years. The letters collected in Letters from Tove trace that romance from its first summer apart, when Tooti became the seed for Too-ticky, the sage of Moominvalley. “I’m so unused to being happy that I haven’t really come to terms with what it involves,” Tove wrote.