Here are a few good links to help you along.
You may purchase ebooks from these fine vendors, among others:
Baen Books: Here’s your link
Angus & Robertson: Here’s your link
BN: Here’s your link
Kobo: Here’s your link
Apple: Here’s your link
Scribd: Here’s your link
You may purchase an ebook OR a paper copy from:
Amazon: Here’s your link
Enjoy!