How I, as a reader, decide which ebooks to buy

This post, rather than being a post on writing, is a post on reading, from my perspective as a reader. Maybe it will benefit other authors in marketing their own books. But mainly, I just wanted to write a bit about how my reading habits have been changed by the “ebook revolution,” and to explain how I decide whether to purchase an ebook.
And yes, my reading habits have been changed by the revolution. For one, I’m reading more, about as much as I did when I was younger. For a bit of background...