This was so much fun! A quick, entertaining YA (6th or 7th grade target, I guess) about girls who work together to solve a puzzle that leads to the ring, and all the clues are set out in the book so one could solve them along with the characters, if only one remembered Algebra 1! It kind of reminded me of The Mixed Up Files of Mrs. Basil Frankweiler, it had a lovely feel to it. Looking forward to the next.