The mass of a book is 1kg What is its mass on the moom?

The mass remains the same despite the conditions. However, the weight would change. The mass is a measure of the matter and remains constant. Weight is affected by the gravity and thus if we say it weighs 9.8 newtons on earth, as a 1kg book would, it would have a weight of 1.63 Newtons on the moon. Hope this is helpful!