The first half of the book uses Java, which you might be more familiar with. The C it uses is fairly vanilla. You shouldn't have to be a C expert to understand it.
Also, all of the code in the book has been ported to a large number of languages:
The book has two interpreters. The first one is in Java. The second one uses C. If you're familiar with Java then it makes for a great learning experience to contrast the Java version with the C version. (I think it's worth it to learn just enough C to be able to go through this second version. It makes for an awesome learning experience!)