The K&R book is still the definitive source on the original C language.
http://en.wikipedia.org/wiki/K%26R
http://en.wikipedia.org/wiki/The_C_Programming_Language
However do keep in mind, that it can only give you some directions and the idea behind the language nowadays, as the language itself has drastically evolved especially during the past few years with the acceptance of C++11 - and C++14 on the horizon.
None of the books for the recent languages would give a good background for C itself though, so I'd say start with that, but don't try to learn it - code in it won't even compile these days unless your compiler is in legacy mode...