Promise of Blood has gone one sale! It's currently $1.99 on Amazon, Kobo, and I think it should be on Nook as well. I'm delighted that Orbit has decided to do this sale. It's a great way for people to be able to get in to the series who otherwise might have balked at paying five times that for the ebook of a new author.
It would also be a good time to remind you that "The Girl of Hrusch Avenue" is available internationally for $.99 (or your local equivalent. This short story is another good place to enter the Powder Mage universe, and you don't have to have read Promise of Blood to enjoy it.