After peeling several popular books on cosmology (And if time did not exist, Big Bang and beyond, our mathematical universe ...), I thought that a book on relativity would help me understand all the concepts that flourished during this twentieth century so prolific in science. Reading is easy, embellished with a few simple diagrams and presents so perfectly accessible to all notions of space-time curvature of space-time and very simply explains the famous experiments (of thought or real) related to this theory traveler Langevin, bend light, Mercury's perihelion displacement ... The book then discusses the impact of the theory of relativity and on cosmology indicates the direction of current theoretical research and experiments in preparation that would highlight the gravitational waves or open the field to a theoretical investigations theory of quantum gravity unless it is the way of non-commutative geometry that provides an answer to the quest for a unifying theory of all areas of physics, from the infinitely small to the infinitely large . We can only regret that this book does not go a step further in his presentation of the theory of relativity. How Einstein has come to E = mc²? What do the Lorentz transformations? Those who already have physical concepts have the answers, but a popular work, which is more to read at the beach, ie without taking the head, could have spent a few more pages to clarify certain aspects "mathematics "theory. In any case, congratulations to the author for having managed the feat to demystify a little bit for the common man, a subject as difficult by giving bonus desire to deepen the subject.