If you have passion for abstract thinking and problem-solving skills, then this puzzle is a great buy.
It may look like it would be straightforward and easy to solve, but it is for the clever (and patient) people.
Solving the puzzle is a challenge. One needs to slide each piece in the correct 37-move sequence to take the Knot apart.
Every move will untangle a bit of the knot. You can buy this for $9.99 at www.thinkgeek.com .