Darknet is a closed network where people share files. See this
Wikipedia article.
Right now, there are no legal digital copies of the series. That means you can't buy it, no matter how much you want to spend money!
First, send an e-mail or better yet an e-mail
and a physical letter (those are much harder to ignore) and let the publisher know that you want an electronic version of the books to read on an e-reader.
After that, what some people do is buy a physical copy of the books and then download an electronic copy from a file sharing site. When the digital copies simply aren't available, people will do this and consider it format shifting as they own legal copies. It's a gray area but many feel that it's morally and legally acceptable when the digital format is unavailable. The key is to make sure you have the physical copies you purchased.
Now, actually giving you step-by-step instructions on how you can grab a copy and from where is against the forum rules.
There are, however, plenty of instructions all over the Internet so a bit of Google-fu should get you there.
As to general instructions on how to get documents other than Amazon's own books onto the Kindle you may want to check out the
MobileRead Wiki. If you still have specific questions, you can then ask them on the forum.
Hope this helps a bit.