What is the best book on the theory of relativity and why is it recommended for understanding this complex scientific concept?

One highly recommended book on the theory of relativity is "Relativity: The Special and General Theory" by Albert Einstein. This book is recommended for understanding the complex scientific concept because it was written by the physicist who developed the theory himself. Einstein explains the theory in a clear and accessible way, making it easier for readers to grasp the fundamental principles of relativity.