Mad C Skillz OEMG

I want to jump to the next level in C. I'm a quite skilled programmer for what I do, know the whole K&R but I feel like I miss something, especially about those weird techniques proPROgrammers use in OS dev and related. Suggested readings?

>>6
>There was also another really book, whose title escapes me, which described the network stack and different protocols at each level in the OSI stack. I'll hop down to the library and see if I can find it again, it was a really great book.

Computer Networks by Andrew S. Tanenbaum?