I like to have a lot of choices when it come time to start a new book, so I have loaded up my Nook with quite a backlog of books - many free, some purchased.
I don't just download anything that's free - I do like to be on the lookout for things like limited time free downloads from authors I like, even if it's a book I already read (for example, the current free download of Melissa Marr's
Wicked Lovely), free downloads from authors I've been meaning to try out (for example
Kelly Link's short story collections), or free downloads that are a genre that I am interested in or just generally seem like a book I might enjoy. Also classics that are public domain that I have already read and loved or that I have been meaning to read.
Something that impacts my purchasing decisions that isn't on this poll is the presence of DRM. If the book has DRM, it needs to be cheap or free, if it doesn't, I'm willing to pay more if it's something I'm really interested in reading.
In terms of what I actually read, if I downloaded it, I'm interested in reading it; it may take me awhile to get around to it because if I see something I'm interested in that's free or on sale, I download it in case the price goes up in the future.