Greenglass House by Kate Milford

Not since Westing Game by Ellen Raskin have I read such a wonderful twisty mystery adventure for middle school and really on up.  Just as Winter holiday is beginning, a usually quiet time for Milo and his parents who run an inn at a historic mansion, one by one a group of very unique folks begin to arrive at the inn.  The include an elderly professor who likes loud socks, two girls with  brightly dyed hair, one red and one blue and an elderly woman who knits along with a Mr. Vinge who is somewhat secretive.  Milo's parents spring into action, bringing in their usual help and laying in supplies for what will not be a quiet vacation for Milo.  Along with the help comes a girl Milo calls Meddy who is an expert at role playing games and who teaches Milo.  From the beginning I wondered about this girl, there are hints that something is off.  Right away there are mysterious goings on such as shadowy figures among the trees on the mansion grounds, someone or several someones trying to be silent padding in and out of rooms, some occupied by guests and some not.
Things go missing as well only to turn up somewhere else.  There is a mysterious map, a recurring theme of a gate seen on a knitting bag, and most especially on the giant very green stained glass window in the house.  There is an impression that each of the visitors has a specific reason for being at the house at this particular time.  The name Doc Holystone, a notorious smuggler, keeps coming up as the original name of the house.  With Meddy's prodding Milo suggests that each guest tell a story to help pass the long evening hours.  And so they do and each story told also tells why the person is there.  They are looking for a smuggler's treasure, anything about the artist who made the stained glass windows, the heritage of a young man once orphaned and adopted and now loved by two young women and maybe other things?  Mostly folks find what they are after though perhaps not the way they expected.  Incorporated into this story is Milo's story.  He is an Asian orphan adopted by Americans who longs to know his heritage, just as the young man Owen, who does learn some of his.
The other characters are diverse as well, old, young, educated and perhaps not and so on.  This makes the book an excellent choice for diversity in books lists.  Since Milo's story is part of the whole story the book should have broad appeal that many diverse books for which the diversity is the story do not.  
JDW10/20/15