I ran across a copy of 21st Century C this afternoon. I hadn’t heard of the book, but the title was intriguing. I wrote more C in the 20th century than the 21st, so my ideas regarding C (sans ++) are out of date. (I’ve written a fair amount of C++ this century, but I have only written C under duress and with difficulty.)
I’ve only skimmed through the book so far, but one thing I like about it is that the first 100 pages are devoted to tools, not the C language per se. There’s a lot more to using any language than the language itself, and I find it harder to learn about tools than languages. It’s hard to know what tools to learn, and what features of those tools to learn first.