The change in potential energy of an object is given by

where
m is the mass of the object
g is the gravitational acceleration

is the increase in altitude of the object
In our problem,

is the mass of the book,

and

is the increase in altitude of the book, so its variation of potential energy is
Answer:
28.3 kg
Explanation:
Assuming the ground is level, the normal force equals the weight.
N = mg
277 N = m × 9.8 m/s²
m = 28.3 kg