The book alone I think is fine. The C code is not compliant with C99 and the author lays out the code and defines variable names in a very non-intuitive/easy-to-understand way.
He drifts around from topic to topic and at times really drags out chapters.
It still has a lot of information that assumes that the reader has prior knowledge about x and y and never really gets around the explaining it.
I'll definitely revisit this book when I'm a bit more familiar with the work and I wouldn't recommend it for beginners in compiler design.
Could've been useful once upon a time, but nowadays trying to compile the code examples is not only a pain the arse, but also nigh impossible. Still, contains some good insight into structuring your C programs and how compilers work.