The Anatomy of a Compiler, 2ed (VNR Computer Science Series)
I can't believe that Amazon even lists this book, as you can see, it's way out of print. I happened to find an old copy of this in my basement (it was my dad's!!).

This was the first book I read in regards to compiler construction/theory. This is mostly a theory book. While not as comprehensive as the Dragon book (from what I've read about the Dragon book), it does discuss Top/Bottom Descent Parsers, context-free grammars, LALR(1) parsing, BNF, and many other concepts.

Of course, you will find the book a bit dated. It uses Fortran in many examples (which personally, I can't stand the language as a language). Having said that though, it did give me a great introduction to compiler theory, something with which to go on and read something else for greater depth and discovery.

If you can find an old copy of this book, it wouldn't be a bad buy for those who need an introduction to compiler theory.
http://www.x45.info/?y8IHu