Hi,
You can buy e-book version for both from amazon.com or publisher
http://www.hentzenwerke.com directly.
Usually, the price from Amazon.com is cheaper (becoz always got discount), but I used to face problem of download the ebook because of security issue. At last, I have to cancel the order and order from
http://www.hentzenwerke.com with abit more expensive.
HTH
I am not the most powerful man in this world.
I am not the worst man in this world either.
I just as same as all of you.
I still need to learn from my mistakes...