I learnt a lot from “Introducing Einstein's Relativity” by Ray d'Inverno and “A First Course in General Relativity” by Bernard Schutz. However, they are by no m

I learnt a lot from “Introducing Einstein's Relativity” by Ray d'Inverno and “A First Course in General Relativity” by Bernard Schutz. However, they are by no means leisurely reads. You need to be prepared to expand your mind (both your physical intuition and mathematical technique) and work very hard (you don't learn just by reading theory, you need to solve exercises and perform long calculations).