General Relativity’ is a fantastic textbook on general relativity with a modern point of view written by Robert M. Wald.
Robert Wald is an American physicist specializing in the thermodynamics of black holes and general relativity. With over 100 published research papers and a contributor to the framework of Algebraic Quantum Field Theory, Wald is a pioneer in the field and presents much of his work in a comprehendible manner making it accessible to non-specialists.
The textbook covers topics from General Relativity (including Einstein’s equations and gravitational waves), black holes and their thermodynamics as well as Cosmology looking at various kinds of universes and how they have evolved.
The book begins with an introduction of preliminary mathematics in the first three chapters which can offer a solid foundation for understanding the rest of the book.
General Relativity’ is extremely reader-friendly and highly recommended for any theoretical physicists. Including excellent explanations and mathematical details as well as problems, it offers a clear and concise background in singularity theorems, causality and black hole thermodynamics.