Did you ever read The Westing Game when you were a kid? Because I did. About thirty times. And now I have read it again.
Even though I had read this a bunch of times before, I couldn't remember the answer to the mystery (although a few things came back to me as I read). I was way too excited by the characters to spend my time piecing together clues to solve the mystery before the book ended, though, so I was happily surprised when everything fell together at the end.
Totally go read this book -- it will only take you a day or so, and it is thoroughly enjoyable.
[And if you have read it, check out this cute little site about the book and the characters, with games!]