This is an informative, very readable, gentle introduction to general relativity, perfectly suitable to advanced undergraduates (it has been designed, and often used, as a reference text to one-year general relativity courses at senior undergraduate level). The book assumes the minimum of pre-requisites, without watering down the subject matter, and without compromising on mathematical depth and rigour.
The approach of the book is pedagogically excellent: after a good speedy review of the main concepts of special relativity, the author develops, in a gentle and highly intuitive manner, tensor calculus in special relativity, and in curvilinear coordinates in Euclidean and Minkowski spaces; he then deals with differential geometry in curved manifolds, and once all this necessary mathematical apparatus is properly explained, the book addresses the concepts of physics in a curved spacetime, until we finally get to the beautiful field equations of general relativity.
Remarkable conceptual lucidity, mathematical rigour and a stress on physical intuition all contribute to an excellent level of readability, supported also by a relativity low number of typos (all very easily identifiable anyway). The concept of tensor is developed with an emphasis more on geometric aspects rather than on transformation properties, an approach that I previously saw employed with some good degree of success by Roger Penrose in his masterpiece (the “Road To Reality”), but to which I personally prefer the more algebraic approach that puts the priority on transformation properties.
Non-Euclidean geometry is similarly introduced in a “constructive”, “applied” way rather than starting as abstract mathematical idealizations, which again is a question of personal tastes and objectives. On the other hand, I really liked how the author adopted the "perfect fluid" model analogy, which I found quite effective in gaining a more “physical” understanding of the stress-energy tensor which is a fundamental concept, as it describes the density and flux of energy and momentum in spacetime, thus representing the source of gravitational field in Einstein's field equations.
In more general terms, critical concepts and items such as equivalence principles, the metric tensor, parallel transport, covariant derivative, Christoffel symbols, curvature, geodesics and many others, are all explained in a concise but mathematically rigorous manner, with derivations that never leave too many missing steps to the reader, who can always complete such derivations with a very reasonable level of effort.
I particularly enjoyed the progression with which the mathematical machinery for dealing with curvature is explored, and how and its associated Riemann curvature tensor (and its contractions: Ricci Tensor, Ricci scalar, Einstein tensor) are all addressed in a very effective way.
The only issue that I have with the author's overall approach is that occasionally too much material is left as exercise to be read and completed in the problem section of each chapter – I strongly recommend that such sections be investigated as thoroughly as the main text, in order to get the maximum benefits out of this book.
Once the field equations are treated, the last few chapters of the book shift the focus to astrophysics and cosmology: gravitational waves, general solution for static spherically symmetric spacetimes, the all-important Schwarzschild metric, quantum mechanical pressure inside a star.
All these subjects are treated with concise clarity too.
Chapter 11 (which I skipped, as not of primary interest to me at the moment, because of their very specific, technical astrophysical/cosmological nature) deals with black holes, perihelion shift and gravitational lensing.
Overall , this is a very good introductory book to general relativity. A good, solid starting point, an helpful and informative stepping stone recommended to readers who then want to get into more comprehensive treatments of the subject, and an accessible and rewarding read.
4 stars - definitely recommended.