I had a first or second edition copy of A Book On C by Al Kelley, Ira Pohl (ISBN 0201183994) which was pretty good (actually I originally picked up C from a Waite Group quick reference, but this book was used as a text in the intro to C class I took aeons ago). Be aware that it's more aimed at a "know how to program and want to pick up C" audience than non-programmers.