my book said the force "push of table" acting on a book at rest on the table is a type of electro-magnetic force. Please explain.?

In the physics world, there are four fundamental forces of nature. These are gravitational force, electromagnetic force, strong nuclear interaction, and weak nuclear interaction. The latter two are short ranged forces and only exist within nucleus of an atom. Gravitational force is long ranged and exists between two masses. Electromagnetic force is that concerned with charged particles, either static or in motion.

The force that you mentioned in your question is termed as "contact force" in physics. It is the force that acts on the point of contact between two objects. It requires "contact" to be enforced. Examples include pushing force, friction ... etc.

When two surfaces are in contact, there is interaction between electrons of atoms at or near the two surfaces. As a result, electromagnetic repulsive force prevents the surfaces to come "further close" to one another. This is the force that we observe and feel macroscopically.

Reference: https://en.wikipedia.org/wiki/Contact_force

Why the atom of the book cannot go inside the table? because there is the repulsion between the electrons of the book surface and the table surface.

I don't know why wikipedia says e-m force is responsible for the contact force. My understanding is that two objects in contact do not fuse together because of Pauli exclusion principle. It is a quantum mechanical effect.