When I was a child in the 80s, there was an old picture book at the public library. It had no text, but it took place in a kind of fairy tale castle on some other planet. If I remember correctly, each scene followed two children as they explored the castle. They may have been following a piece of yarn that eventually led them to where their mother sat knitting in one of the castle rooms or towers. There may have been a sort of robotic-looking cat playing with the yarn at some point. I remember the artwork as being full color paintings like you find with 1960s scifi book covers or movie posters.