Yes, I second the recommendation for the colored fairy books. They are collected & put out by Andrew Lang. They contain what I would consider "classic" European fairy tales which is to say they are pretty Anglo in their outlook. If you want to go for more specific mythology and folklore, "European" is honestly a pretty broad category and I would consider breaking down more specifically via region, aka, Scandanavian folklore, Irish folklore, Roman/Grecian, etc. I'm afraid I can't recommend anything on Polish folklore in general but I think a quick search on Amazon should yield something like what you are looking for.
I read some of the books by Andrzej Sapkowski, the book series which the famous "The Witcher" games are based on. I heard they are based a lot on Polish Folklore, and it left me craving for more. I said European because it really doesn't matter to me, since I will probably want to read most of it. Thanks for the reply!