Just a month ago, I made some pretty interesting analysis on how far things have reached the level "information should be free". Frankly, after what I saw, your case looks as a quantum event over the whole Universe. Yes, I understand your feelings, more, I understand that you feel pain to see your child running wild after so much of your life spent on it. But... You cannot change a tide that is more than just "Internet". In fact, the problem is not on Internet "per se", it is in a lot of things that have been running quite wrong for, at least, the last quarter of the century (maybe a little bit longer, imho).
The big problem is that information, today, costs zero, nada, null. Not in terms of traffic, pdf, ebook or that effort you made to create your book. It costs zero to the crazy "digital" society that you, I and everyone else is in. For the 99,99999999% of the people around us, it is not a big difference you wrote a book or not. More, for 99,99999% of those, who have some say on matters of management, administration or state politics, your book means nothing at all. Yes, you may think that these ones may rise their eyebrows, for the fact that someone violated your author's rights. However, before you consider your lawyer the author's best friend, please consider this question: apart of the monetary value of your book, can he consider any other values the book may have? Sincerly, I'm pretty sure that he will not make no difference between "compression" and "cooking". And that is exactly where the problem is and that is why your book finds a way out only in a pirate network.
Someone may counterargument that lawyers have not the duty to know what "compression" is. Yes, as 99,99999999% of "everyone" does not have such obligation. Who remains? A miserable fraction of weirdos who are really interested in such matter. Now, pick up the environment where these weirdos live in... And you immediately understand why piracy is the law of the day.
What Google is showing is not millions taking your book for free. It just a few hundred under the complete indifference of six billion people. That's the Truth out there.
Now, why a few hundred is doing it? Because things have gone too far and it is too late to stop it. Frankly, don't take this as an offense, but "compression" - it's not serious. Want rockets? WMDs? Fighting instructions? Weapons of all kinds and sorts?..
Do you want how to build the?.. Which one?..
And you don't need to stop just on the horror side of the story. If you are romantic enough, you can go for robots, nanos of all sorts, genetics, AI and the 100001 ways of programming. You can go also for many other things, from paleontology up to the prototypes of nuclear fusion reactors.
"Compression" is just a drop of water in the middle of the tide. Your book is nothing inside the tsunami.
Just to give you an idea of what I am talking about, I would remark that only one of these mega-libraries carries more than a hundred thousand books. And the "knowledge base" ranges mostly from 19th century up to our times. And I would not think that this large base carries a "expired" term. An AK-47 prototype is an AK-47 today (47 is the official year of its creation). And rocket mechanics work today the very same way they worked half a century ago.
Yes, programming goes a little bit out of this. But can anyone be sure that it "goes"? Maybe it "looks" more than really "goes".
Now this is the "industry". In some way it shall be justified - lots of books have long been out of print or were nearly lost, if such libraries didn't start to thrive, On other way, we have to consider a balance - books shall be bought, but are they easily affordable? And, in the end, we shall consider that there is an innerent danger under all this - a big chunk of this knowledge carries heavy consequences.
Now what one shall do with this? That's the billion dollar question. But, the thing I'm sure no one shall do is "hunt and prosecute". These "wars" have only made things much worser than before. Besides, it is absolutely no secret that the "War on Terror" boosted the "Weapons Section" of all these libraries. I have been here for many years and I clearly saw how three jerkish decisions, made by shadow smarties in a big capital, led to the mushrooming of "Army Manuals" all over. And now, 8 years after 9/11, we even have "It" on the Net! Another such war will only lead to new hideouts and new mushrooms. The result? No, sorry elephants but no Pearl Harbours here. Yes, we may get a nasty mushroom but I would be very sorry for the guy who did it. Because the thing demands a some Hell of gray matter and megatons of work. That's the good thing of these libraries - it shows that things are really not so simple. Really, they are quite far from simple. Besides they show you're will be more likely a fried duck rather than the Evil Genius five minutes after you do "It".
Yes these are high waters and you are only concerned about your book. You still can go this way. You hunt your own people not to read your book if they didn't buy it, But, what will the "others" do? Avoid reading? Be politically correct? Ok we read about how to build rockets but "compression" ist verbotten.
When, in the History of Mankind such thing happened? Portugal "hold" the South Hemisphere as the best kept secret for nearly a century. Inquisition came to Portugal, made a huge mess with all sorts of books... And less than 30 years they lost everything to the Dutch, the French and mostly the English. Now, you make your small "Copyright" Inquisition. You may get some success for a year or two. But don't get shocked that in 30 years, no one remembers you except the chinese, indians, pakistanis and iranians.