Tom Sawyer and the Buried Treasure, by I. M. Richardson, Troll Publication, 1984.
I found this book in a thrift store for less than a dollar. It looked interesting, so I bought it. While the text in this book doesn't have the flair of Twain's original, it is a good introduction to the Tom Sawyer character for younger readers. It is of one of the most memorable scenes in Tom Sawyer. And the illustrations are appropriately dark and tension-filled.
I'm hoping that since my son likes this book at six, he will love Mark Twain's Tom Sawyer at ten.