Thanks to those who alerted me to not being able to find Angelfall for the Nook. I've been told it should be available in a couple of days. Thanks for your patience!
[--Sept update -- Strange things are going on at BN. They had the Nook version up for a few days, then they took it down. I don't know what's going on. Their paperback version is currently $3.61 and qualifies for free shipping. So you could go that route. So sorry about the Nook snafu! Hopefully, it'll work itself out soon.--]