This book was a little over my head when I was around 7 (ironically). It was not a Little Golden Book nor a Disney book!
It was a story book or what seemed to be a collection of related stories. An elementary epic? May be Scandinavian stories rather than Soviet.
The early 1970s edition I had was bright blue and the cover was at least 8 ½ x 11.
There were seven (or only six) sisters. In the picture book version each sister was wearing an ornate but monochromatic dress. I’m thinking they were different examples of the regional dresses worn, or maybe clan-type styles. But with a hippie-vibe art style.
I think each sister was sent out on some kind of unusual coming-of-age search. Or maybe they were kidnapped by seven (or six) different people and each had a story about how they got home.
I was a natural reader, but either the words were a bit too big for me or I was too interested in what they were wearing to remember much of the plot. (That, and home wasn’t peaceful so I was sleep-deprived…so it was a big, wordy, beautiful blur of a book.)
I’d still have the book, but since I didn’t seem to be reading it, Mom gave it away to charity. I still have books that I was given when I was even younger…