By far the best book about General Relativity and its connection to Cosmology. I used it to learn for a GR oral exam and a Cosmology oral exam and got an A in both. But more importantly, I really enjoyed reading it and there are so many explanations here that can't be found anywhere else. While other books seem to be lost in details, Cheng manages to get straight to the point and explains lucidly why the concept beeing discussed is important. I tried to read Weinbergs classical book, but found this book much better