Where do you buy your ebooks? Because it matters to the authors.
The best place to buy them is at the publisher's website. Why? Because authors get paid by the book, and they make their best percentage at the publisher's website.
Some publishers are even offering immediate discounts on new releases. For instance, Whiskey Creek Press has each new release at 10% off the first three months.
I know a lot of people wait until the book gets to Fictionwise and ARe because they have an account already established with them. That's okay. Authors get paid the least from those bookstores, but they often sell the most books there.
Either way, buying a book is the best way to tell an author, "Keep writing!" To which we reply, "Keep buying and we will!"