General relativity is wonderfully interesting and extremely important. It is a difficult area to learn well. At one extreme, a lot of popular books avoid all equations and give only imprecise (sometimes incorrect) qualitative notions of what it all means. These are not very good. At another extreme, you might expect to master all of Riemannian geometry and modern manifold theory just to get a start. This is a wonderful little book that manages to find a useful middle ground. It shows you enough of the real mathematics to get you started. That is much more important than it appears because it lets you do further study with more insight concerning what is important. It gives you a very clear notion of what it all means and is certainly the clearest currently available introduction that could lead to useful speculation about quantizing gravity. It is certainly a non-trivial read, but it is clear and concise and, most importantly, correct. Many very useful books are boring to read. You could need lots of coffee. This one is pleasant and will only require as much coffee as you like anyway.