free or pay what you want
I have given a lot of thought to the nature of digital products. Although the digital formats for all my books are available for roughly $5 on apple, kindles, b&n, etc., I agree with Corey Doctorow, that files are files and files are meant to be copied.
There is a growing movement in the digitial community that files need to be commodified via the blockchain. If you are familiar with any of my work, you might guess that I disagree with this idea. Not only is the commodification of information a backwards move for the web, the commodification of everything has led us to the mess we face today.
Therefore, you are welcome to purchase my digital books, and eventually, my audiobooks, on a pay what you want, including free basis. If you do so, I would appreciate that you sign up for my newsletter, but that is not required. If you want to support me monetarily (and I encourage that, since it helps me live), please become a patron of my work at Patreon.com.