I used to avidly reverse engineer the IOCCC entries when announced. It was a wonderful learning experience that teaches you quite a bit about C that you don't get from a mainstream book. Time well spent.
"Obfuscated C and Other Mysteries" by Don Libes
"C Companion" by Allen Holub
Don Libes' book actually uses Obfuscated C code entries as interesting instructional examples and Holub's book is a nice intermediate book between K&R and "Expert C Programming".
I never see Holub mentioned much by other C programmers but I think his books are awesome. He actually also has a really good compiler book called "Compiler Design in C" that showed how to build a C compiler from the ground up - with a lot of practical details I never really see in other books in that area. He even had a cool curses implementation to go along with it where you could watch the parsing occur visually, and wrote a curses-like library in assembly so you could run it all on DOS too. He used to write the C Chest columns for Dr Dobbs back in the day and the book "C Chest and Other C Treasures" contains a collection of those articles and other code that C programmers would find interesting. But that book is harder to find these days.