Foundations of General Relativity Text - Recommendations

[dEdt]

I'm looking for a good text on the foundations of GR. Geared towards physicists, but with a focus on the subtleties of the ideas that went into building the theory rather than on applications. Any recommendations? Thanks!

 

[Naty1]

For a beginning look, try Einstein online and read [online] Einstein's own book RELATIVITY for an interesting introduction to basics with HS math.