Experts I am not able to understand this paragraph.. (from when..... to weight) .. I mean what is it trying to say??? Pls explain it to me in a lucid and direct manner.

Dear Student

It means to say that when we hold a book, book experiences gravitational force according to Formula
F=$$\begin{gathered} G\frac{mM}{r^2} \\ where m is mass of book and M is mass of earth \end{gathered}$$
It is balanced by force of our hand which pushes it upward and contact forces can be termed as electromagnetic forces.

Regards