I really love this Hungarian book by Éva Janikovszky from 1969 that I found in the thrift store some while ago. The illustrations are so fine, fine, fine with the mix of water colour, thin black pen and beautiful, neat patterns. We don't read Hungarian, of course, but we do read the book anyway, just guessing us to the story and finding new little details everytime we "read" in it.
Here is another nice book in Hungarian.
Update: Saskia from fine fine books has pointed out that the illustrator is László Réber. At first I wasn't sure who made the beautiful ilustrations, because I couldn't read the Hungarian colophon - so thanks Saskia :)