content: This was my first O'Reilly book, and one I've used ever since as a yardstick of what they're capable of producing.Faced with the daunting task of writing a compiler, I discovered this book and was amazed at the wealth and depth of information it contains.It could possibly do with a little extra theoretical background, but if you are looking at any sort of task involving lex and yacc or their derivatives, buy this excellent book.