Your assumption on the right prenounciation is close to perfect. In Denmark (neighbour to Sweden) we would spell it "VÆSEN" Æ is A and E put together. The sound in the word "Veil" (ei) but without the distinct "i" sound pretty much the sound of AE/Æ. Hope this helps everyone.
Year zero engine takes its name from Mutant Year Zero. And that Mystery chapter is complete gold, really useful advice for crafting scenarios, a lot of it applicable beyond Vaesen mysetries. I've written a couple already, mostly just going off it like a formula. In the process of streaming the second of the mysteries I've written on YT. It's such a pretty book and those dice are now my favorite d6's. But yeah, this is my favorite iteration of the year zero games so far. I also totally agree that the Vaesen not just being "monsters" is refreshing and the themes of social upheaval by the industrial revolution is a gold mine of inspiration. Thanks for the review!