I think to have a decent understanding of c, or start learning c programming is really good even if somebody is not planning to work with the language itself. Most of the languages are based on c or are in some way related to it. Most of the currently used popular languages have at least the syntax related to c.
This book can give a really great start on understanding and writing basic c functions. It has exercises what are really handy, I actually wrote them all what gave me a great advantage in college projects. There are cases when you find yourself stuck at few of them but there are many solutions available only. It can also give a different view for those who already know the language.
I am a Software Engineer with a keen interest in security, applied cryptography, cloud computing for highly available systems and everything in between.