/diy/ - Do It Yourself

So, recently started getting to the machining field, and I've seen this book recommended as a resource. Question is, is the newest edition really necessary? Or is it like college textbooks where they change a picture and a couple sentences, then call it a new edition and sell for as much as they can squeeze out of you? And if that is the case, how many editions can I go back and still be useful when working with metal?