If you are looking for an introduction to Unix, this is the book you're looking for. If you're looking for an introduction to ANSI C, again, this is probably the book you're looking for. If you want one book that will introduce you to both, well, this is the only book you want.
As a testament to the stability of Unix, the last edition of this book was made in March 1984, and it is still useful today. It will introduce you to the bourne shell, sed and awk, and the C programming language which is/was so central to the Unix concept. It's written by two old the oldest names in Unix, and one of them is a father of the C language. The examples are all well-written and simple, and since they are very simple, should work fine with pretty much any compiler. Certainly, I had no trouble with any of the examples on a modern Linux distribution.
Whether you've been using Unix for a little while but still haven't caught on to the true power of the whole thing, or have never touched it at all, this book can give you enough material to become comfortable with the shell environment. It will teach you a little bit about everything important in Unix in terms of core concepts, and provide you with a solid foundation to build on.