Started off so well, with delightful lines like
"Shabby in a gentell way, as if the people who lived there didn't have to keep up with the Joneses because they themselves were the Joneses."
But the momentum just didn't stay. I loved that the story involved Nazi-stolen art and smart kids and funky grown-ups, but it just didn't feel right. There's a museum director as a character who is completely unlike any museum director I've ever know (not in a good way).
And the ultimate resolution, while satisfying, almost felt false.

Just doesn't have the same magica as other Konigsburg, though it's still Konigsburg which makes it better than lots of kidlit.