Answer:
The normal force is the force that a surface makes on an object that lies on that surface.
As the book rest flat in the table, the force acting on the book will be the gravitational force. This force pulls down the book against the table, then the normal force will be opposite to this, then the direction of this force is upwards. Being more exact, the normal force always acts on the normal direction to a given surface, to find the normal of a surface, you need to find the plane of the surface, then any perpendicular line to that surface will be "normal" to the surface (and the normal direction points away from the surface) then if the book is resting on top of the table, the direction of the normal will be upwards..
Then the force that acts on the book is normal to the surface of the table,