The rules are fairly simple. Each turn you have two possible actions and two possible ways to move. On top of that you cast spells to help you and exchange books with other players in your current time. That's it. The complexity arises when the players try to solve the challenges ahead of them. Challenges that require them to use their resources, magic and time traveling sensibly.
The time travel mechanics are of course central to the game and are approximately equivalent to the mechanics known from Harry Potter. That is, anything observed is unchangeable but everything else can be changed. This means the players have to make sure that everything they observe actually happen which may lead them to having to place the same book back twice at the same time or other strange and challenging situations.
Remember a paradox is only a paradox until you fix it and nothing lasts forever..not even time travel.
Mechanics: Time travel (simulated...), tile laying, puzzle, cooperative