If you're just looking for a cursory introduction to the underlying concepts, I agree with the other comments that K&R is what you are looking for. I'd add the

If you're just looking for a cursory introduction to the underlying concepts, I agree with the other comments that K&R is what you are looking for. I'd add the caveat that due to the fact that C is a tiny language with a tiny standard library, most code you'll see in the wild uses custom concepts/libraries/object models on top of C. So for most practical purposes, there isn't really "C" as much as there is "unix programming C", or "embedded C", or whatever else have you, and all of them add a thick layer on top of the core language.