I am looking for reading material recommendations for over the holidays.
Is the K&R book still relevant, should I pick it up?

found.

Unless you're already very comfortable with all of ANSI C, it's definitely still relevant even today. It won't expose you to any C99 (VLA, improved printf, restrict, etc.) or later features, but if you're compiling with MSVC you don't get to use most of that stuff anyway.

It's still relevant. It is especially popular for its interesting code snippets and exercises that will make you think and learn something (no mind-numbing exercise there).

If you're looking for something that is more like a reference, I like The C Book (http://publications.gbdirect.co.uk/c_book/) which has the advantage to be free. It also doesn't cover C99 though.