Answer
The heavier book would have more kinetic energy.
Work Step by Step
When objects fall they are all acted upon by gravity and accelerated at the same rate (9.81 $m/s^2$). If a heavenlier book fell from the same shelf, it would have the same velocity before striking the floor but since Kinetic Energy = 1/2 $mv^2$, the velocity would be the same but the mass would be larger so it would have more Kinetic Energy
