|Weness says you should download the book right away!|
Smashwords -- Available in HTML, Epub, LRF and more.
Amazon -- Available in Print and Kindle versions (If you buy the paperback, you get the ebook for free!)
Barnes & Noble -- Nook version
Kobo -- So you can read on your Android and other devices (Aussies, take note!)
I also believe it should be available soon in the iBookstore, Flipkart, Diesel and some other places. But, let's be honest, if you buy books it'll be at one of those four places, right?