I'll assume you have the proper mathematical pre-requisites. A first book to get a feel for what relativity is all about would be Russell's ABC of Relativity. I liked it in high school when I didn't have a very strong mathematical background past multivariable calculus.
I then learned special relativity through the first chapter of 'A first course in general relativity'. I don't really know any other exposition of SR except 'Physics through symmetry', which in my opinion isn't exactly enough. As for general relativity, I haven't learned it yet, so I won't comment on it.