The constraint: You may only move groups of three adjacent books. They must all be moved at once, without changing the order. Note that once you move a group, there are three empty spaces left behind. Books with spaces between them do not count as adjacent. Neither the starting or ending positions should have any empty spaces.
Try to do it in
This is based on a similar puzzle in the game 11th Hour. The puzzle in 11th Hour was essentially the same, only that you move groups of two adjacent books instead of three.