Now this is a unique puzzle. Dewey's Dilemma is a puzzle consisting of 12 books. Can you arrange them on the shelf without having any consecutive numbers, no two books by the same author, or any books of the same height next to each other? Each of four authors has three books made of a different hardwood. With so many variables to keep in mind, this puzzle is a real challenge. With additional difficulty added by taking books by one author and placing one at each end and one in the middle, you can challenge yourself with up to 21 more unique challenges.