The title ‘Skurken i Muminhuset’ translates to ‘The villain of the Moomin house’. It was published in 1980 but has never been officially translated into English.
The pictures found within the story are all photographs taken by Per Olov Jansson (Tove’s brother) from within the Moomin house which was constructed by Tove Jansson, her partner Tuulikki Pietilä and Pentti Eistola in the 1970s. This is now situated in the Moomin musuem (muumilaakso) in Tampere art gallery, Finland. The story of its creation is available in the museum, but photographs are not permitted. The next time I go, I will write down exactly what it says.
Teresa Ronayne has kindly translated the text into English on their website, which is available here. I would highly recommend that it is read before visiting the museum, as you get a better idea of what Tove was thinking when she created it. It is honestly the most intricate and beautiful piece of art I have ever seen.
It is hopeful that soon, an official translation will become available. Bare in mind that even now, almost eleven years after Tove’s death, her books are still being translated.
Here is a picture of the house, taken from the blog http://moomiest.blogspot.com/