I read it in danish around 2008, but I don't think it's originally danish. Also by "kids" I would say 10 , because they're still scary in a way, but out in the children's section of the library.

I remeber that the first one was a boy that starts helping an old lady, I believe with groceries and such? And she has a beautiful painting on her wall that they talk about, and I think he comments on how lifelike it is, and at the end of the story he gets sucked into the painting, and it's revealed its lifelike because all of the people in it are people she sucked into it.

There was also a story about a man doing something in the basement of an apartment complex, I think something with Rats or cats? And another boy begins talking to him, and as the story progresses, the man gets more and more animal-like until he turns into an animal at the end if I remember correctly, and the big climax is that he catches the boy I think? And makes him undergo the transformation as well... either that, or it was the boy transforming all along.

The only other one I remember bits of is one about a doll and a girl, and I think theclimax is that she's transformed into a doll as well and she's horrified about the fact that she can't move anymore.

There were other stories in ot, but these are the ones I remeber the best. Tbe cover (at least in danish) was very dark, I'd say black. I want to say yellow writing, but I'm not sure at all. Hope you can help me!