Thumbs way up to the ceiling!
This is one of my favorite books. I read this for school in 6th grade and then spent a year searching every Goodwill in the Twin Cities area for it. I hadn't had a chance to reread it since my children were born, but recently took the time to revisit it in preparation of sharing it with my oldest, who is 9 (who loved it too).
The book starts with a group of strangers moving into a new apartment complex- some of which have children. A famous businessman, Sam Westing, is found dead. Soon after, they are all summoned to the reading of his will, which says that one of them murdered him. The will outlines an elaborate "game" which the "players" need to follow to discover the identity of the murderer and get the proceeds of the will. The book primarily follows the attempts of the kids to solve the crime, and a girl named Turtle in particular.
Paging through this mystery, even as an adult, is a treat. It's one of those rare books that you reach the end of, then immediately want to reread it to see how everything unfolded in light of the information gained in the last chapter. This smartly written book is like a logic puzzle in prose and an excellent choice for readers- young and old alike.