I'm happy to announce that as of today, The Valkyrie is now available on Nook! I will likely add The Goddess Denied there in a week.
The process of uploading and publishing to Nook has been a learning process. The maps and runes between each section had to be stripped out, as well as the appendix on bindrunes, due to upload space constraints, which makes me a little sad, but I like how legible the previews are, by and large.
So if you have friends who haven't wanted to give it a try, since they're Kindle-app-averse? It's now on Nook!