A Short Course in General Relativity
James Foster, J. D. Nightingale
This textbook provides an excellent introduction to a topic that is extremely easy to get bogged down in. I took a one semester course that used this text as an undergraduate, during which I thought the book was merely decent, but then when I took a gradute course that used Carroll's Spacetime and Geometry is when I really came to appreciate the preparation this book gave me (not that Carroll's book is bad, I just wouldn't recommend it for a first reading). Not to mention the book is pretty cheap as far as physics texts go.
