The Dragon book is a classic because it was the first book in the field of any significance, not because it's actually any good. (Consider it a classic compiler book in the same way that "Plan 9 from Outer Space" is a classic SciFi movie) Everything you need for a simple compiler is in there, but you'll get it out with far more pain and confusion than the subject warrants. Newer books in the field, such as Modern Compiler Design by Grune, Bal, Jacobs & Langendoen (just off the top of my bookshelf), are much better and far easier to read.