Resorting to the metaphor of "bongs of a bell" to describe differential forms and "machines" to introduce the notion of tensors is a little insulting to capable undergraduate physics students. This is one of the most overhyped and overrated textbooks I've ever used.Physics and math students: Brush up on your vector calculus and classical mechanics and start with Shutz's "A First Course in General Relativity". If you've had some general relativity already, head for Wald's "General Relativity".