The Art of Unix Programming is full of general advice. It's an easy read and a majority of it is potentially useful even if you're not interested in Unix-like systems.
I found it enjoyable to read, although ESR is very opinionated. If you've read How to Ask Questions the Smart Way http://www.catb.org/esr/faqs/smart-questions.html
And appreciate the content despite the issues with its delivery, you'll probably enjoy the book.
Good book, but note it's about design, not implementation:
You should not read this book if what you are looking for is the details of C coding or how to use the Unix kernel API. There are many good books on these topics; Advanced Programming in the Unix Environment [Stevens92] is classic among explorations of the Unix API, and The Practice of Programming [Kernighan-Pike99] is recommended reading for all C programmers (indeed for all programmers in any language).