RELATIVITY: THE SPECIAL AND THE GENERAL THEORY aims to give, as Einstein himself says, an exact understanding of the concept of Relativity to the readers who are interested in the theory but are not conversant with the mathematical equipment of theoretical physics. When he wrote the book in 1916, Einstein was not as well-known as he is now. This principal work not only made him famous but made him the greatest physicist of all time. The new theory of gravity and different perspective on the cosmos establish this work as a pioneer in the world of physics.