I read K&R 20 years ago and today it's still the closest programming book to my heart -- yeah there's more modern choices but the exercises are unmatched, it's short, and it's one of the most fun books you'll ever read.
The standards for C99, C11 are open. Look up what you don't learn in them and grab one of the other more modern suggestions from here for that, but K&R is a must have for any C programmer.
You probably won't be able to put the book down if you start reading it.
Technical aspects aside, K&R has what some modern books seem to lack: a really clear and comprehensive layout. I've picked up a few modern books and immediately noticed how they make use of thinner (thinner != smaller) fonts that make then hard to distinguish.
At first I thought it was my fault for being old and wearing glasses, but as soon as I opened back some other old books like the K&R, the Niklaus Wirth (Algorithms+Data Structures = programs) and a couple other ones, I could read again without effort at the same distance wearing the same pair of glasses. Why do they use fonts that thin today?
The standards for C99, C11 are open. Look up what you don't learn in them and grab one of the other more modern suggestions from here for that, but K&R is a must have for any C programmer.
You probably won't be able to put the book down if you start reading it.