The Game of Sunken Places - by M. T. Anderson

This is a creepy book.  Two teens accept an invitation to a distant uncle's mansion deep in the Vermont woods, and when they get there realize that they're being pulled into a game like they have never played before.  Their first clue that something odd is afoot is when the uncle takes their clothes away (and burns them) and gives them starched shirts and knickerbockers to wear, as if it were hundreds of years earlier.  When the boys find a mysterious game board in their room and start to play, the wheels of something grand and terrible are set in motion.

This story follows friends Brian and Gregory as they battle forces of ancient darkness in a game neither of them really understand, but which has consequences as great as death itself.  Mystical creatures appear in the woods, mysterious messages need to be deciphered, and both boys must call upon every bit of their courage to make it to the thrilling end of the game, where they realize they were fighting something else entirely.

This is a great adventure, a thrilling collection of twists and turns that will chill you and delight you simultaneously. It has a slow start, but creeps along until you are totally sucked in and going mad with questions that don't seem to get answered quickly enough.  If you like creepy adventure stories and games, this is your book!