Are the neutral and ground of a receptacle connected, my book says that ground is zero potential

thanks

Yes, the neutral and round are generally connected together, often at the point where the electrical service enters the building, but nowhere else. This ensures that the neutral potential is close to that of the local ground, and also prevents ground loops, which are currents flowing through the ground, or ground wires, between various loads.

NO, it never allow to join earth terminal and neutral terminal together at any receptacle.