One widely recommended book for understanding the theory of general relativity is "A Brief History of Time" by Stephen Hawking. Although it covers a broad range of topics in theoretical physics, including cosmology and quantum mechanics, it also provides a clear and accessible introduction to general relativity.
Another popular choice is "Gravitation" by Charles W. Misner, Kip S. Thorne, and John Archibald Wheeler. This comprehensive textbook delves into the mathematical foundations of general relativity, providing a thorough understanding of the theory. While it may be more technical than some other books, it is highly regarded as an authoritative resource.
"General Relativity: An Introduction for Physicists" by M. P. Hobson, G. P. Efstathiou, and A. N. Lasenby is another excellent option. It offers a more beginner-friendly introduction to the subject, focusing on the physical concepts and providing intuitive explanations alongside the necessary mathematics.
If you prefer a book that takes a historical and conceptual approach, "Einstein's Relativity and the Quantum Revolution: Modern Physics for Non-Scientists" by Richard Wolfson is a good choice. It explores the development of Einstein's theories, including general relativity, and how they revolutionized our understanding of space, time, and gravity.
Ultimately, the best book for you will depend on your background, mathematical proficiency, and the level of detail you seek. It's a good idea to read reviews and sample chapters to find a book that aligns with your interests and learning style. Additionally, online resources, video lectures, and courses can supplement your reading and provide a more interactive learning experience.