The Hidden Boy, by Jon Berkeley, is a fantasy story about a family who wins a "Blue Moon Once-in-a-Lifetime Adventure Holiday" to a strange land called Bell Hoot. 
When they arrive, however, they find that their 7-year-old son, Theo, is missing, and that they can never return to their previous home. Bea, the missing boy's older sister, seems to be the only one who has a chance of locating Theo and setting things right. Evidently, Bea is gifted in the use of Mumbo Jumbo. I'm not sure if Mumbo Jumbo is a language, or a magic, or what, but for Bea it has something to do with an ability to communicate with bees by humming.
The story includes many interesting characters, but I had a difficult time understanding all the rules of this strange world. There is a rule that only groups of seven are allowed on the transport vehicle, which is a cross between a bus and a boat, but after finishing the book I'm still not sure why. Also, Granny Delphine owns a pair of glasses that allow her to see things that others can't, but I'm not sure why she is so special in the family. I guess I felt as though I were reading book two of a series and had not read book one yet. Consequently, I thought the book was interesting, but it didn't grab me as others have.
What I liked best about the story was Bea's ability to communicate with bees. She has the ability to communicate with them and influence their actions, but more importantly, she understands their culture and the important role they play in nature.
I think I will add The Last Treasure, by Janet S. Anderson, to my recommended list for middle grade mysteries. 
This story's main character, 13-year-old Ellsworth (Zee) Smith, gets a letter asking him to come home to the Square in Smiths Mills, NY, because his family needs him. Ellsworth and his dad, Ben Robert, left the Square many years ago, right after Ellsworth's mother and baby brother died. Since then they have lived many places but have never returned home. However, now the family needs Ellsworth's help finding the last of three treasures that the family patriarch, John Matthew Smith, left. Ellsworth's father does not want him to go but finally allows it. When he gets to Smiths Mills, Ellsworth meets his cousin, Jess, and together they work to solve the puzzle of where the treasure is and how to get to it.
This is not a murder mystery, then, but a puzzle to solve, and the ending is quite satisfying. The story revolves around family and the importance of resolving conflict among family members, even if -- or especially if -- those conflicts have been festering for many years. There is a lot of family history to explain, going back to the 1800's, so the book starts out a little slow, but it picks up quickly. I enjoyed this story very much.
