How good is this book for a complete beginner? I am starting to learn C in my free time and I have no objective way to judge this book.
That being said I'm not entirely convinced that implementing a programming language is the best toy project for learning C since one of the first things you have to write is a parser and we all know string handling in C is a pity.
That being said it looks very interesting, I know C quite well but I might read it for the "implementing lisp" parts.
However, if you're serious about learning C then I strongly recommend getting the K&R book [0]. It's short and quickly gets down to business --- the first chapter alone gives you a condensed but working overview of the language as a whole.
Even experienced C programmers seem to keep the book around as it's good as a reference as well.
I strongly recommend people to learn C. It's a small, beautiful and very powerful language and the lingua franca for language ABIs. In fact, many popular dynamic languages are implemented in C (Python, Ruby, Lua and countless others).
Your time will be well spent!
[0]: http://en.wikipedia.org/wiki/The_C_Programming_Language
Both K&R and "Modern Approach" lack that word "Modern" very much, yet are written with undertone "it's everything you have to know about C", when it isn't. Person who doesn't know C very likely doesn't know how OS works, what architecture layers are behind the software he uses every day. He just knows somehow he wants to learn C, but doesn't really understand what C is, yet he knows that virtually everything is written in C, and "everything" usually doesn't run in terminal, but processes and produces sound, images, video, can have GUI, use some external devices, run in parallel, run on GPU. Also, it's pretty obvious (especially if you've used some language like Python already) that nobody writes everything from scratch these days, but there're many libraries that proved to be useful.
And stuff like branching and cycles seems to be pretty obvious even for somebody without coding experience, as far as I can judge from what I've seen so far. Yet we have plenty books that spends 20 pages to explain "if" keyword and mentions every function in standard library (why?! it's 2014, people, we have cplusplus.com now!)and covers nothing in sense of what useful libraries are out there, what are these domains where you still should use C today (because feet to meter converter shouldn't be written in C today and you probably should choose Python if there's no specific reason to use C), what tools to use for testing and debugging and such.
And while it can be justified for K&R (jeez, how old is that book!) it's just ridiculous that book that has "Modern" (well, it was 2008, but still…) in it's title covers almost nothing of what person who wants to program in C should know today. Worse, you'll see that only after reading these 800+ pages.
"C the Hard Way" is a little bit better, but still not as good as this one. This one also isn't perfect, but is the best of what I've seen so far.
I would think that either way you can learn C. Which way is better for you depends if you are more motivated by going through one long project, or if you prefer to have many small ones.
In fact, for me it seems to be the best thing about this book. It mentions everything you need to hear once to be able to use search engine and clarify anything you don't understand. So help yourself! You don't know syntax of "switch" statement? Google it (or duckduckgo, or whatever)! You don't know how to use printf? You've been shown the way to cplusplus.com already, take your time and find out everything you want to know about that function. Then come back for a new piece of information to think about.
The only two things I guess are missing is "make" (I'd mention it from the start to help everybody save some time, with gdb and valgrind) and a little bit more information about pointers from the very beginning, because searching for help about "free" function will be no good if you don't know about stack/heap allocations.
For real world projects, it's not a bad idea to implement your own memory manager (even if it's only a wrapper for malloc and free). For real world interpreters Lua (www.lua.org) is written in C, is quite widely used and is not too large - if interpreters are your interest. If you are into lisps Structure and Interpretation of Computer Programs http://mitpress.mit.edu/sicp/full-text/book/book.html contains a the instructions for writing a lisp interpreter in any language.
In particular, Lua uses no intermediate representation (there is no Lua AST!), which makes its compiler portion a quite confusing read. Its interpreter portion is no less confusing, being a register VM with a register window scheme and a non-recursive eval using goto and a separate call stack. Do not be fooled by "not too large" aspect. Lua is worth studying, but it is definitely not a beginner material.