I am not recommending any books on C (because I don't know about any, and also because I mainly do C++ rather than C).
Now if you are a beginner:
If you go on the link given below, you can download the DEV compiler, which compiles both C and C++.
The link is: http://www.bloodshed.net/dev/devcpp.html
Out of the three download options, choose the first one ( 9 MB download).
The best thing about this compiler is that it has got its own full-fledged tutorial on C, which takes you from the most basic to the most complex.
Just download the file, install it and run it. Click on File -> New -> Source File.
This will open a notepad-like file inside the compiler on which you can write the code. After writing the code you can just click on Execute -> Compile and Run.
To get started on the tutorial, just go to Help -> Help on Dev C++.
The tutorial will be a good starting point for you, after which you can advance to the books recommended by other members.
This is how I first learned C. After learning C, it is very easy to adapt to C++ (you will find that yourself).
However, if you are not a beginner, and just want to increase your field of knowledge of C, then you don't need to do anything written by me in the above lines.
regards
Mr V