The Reluctant Amazon by Sandy James is free right now. I squeed, and downloaded it when I found out since I have meant to read this series ever since I first heard about it.
Right now we are seeing the effects of the loss of Agency pricing. Several big publishers have discounted Fantasy and Science Fiction.
Harper Collins have discounted a lot of fantasy and Science Fiction e-books right now. Among them is Snuff by Terry Pratchett, The First two Long Earth novels, the first two novels in Sean Russell’s the Swan’s War series. Three Sheri S. Tepper novels… There are probably a lot more available
Del Rey also offers a lot of books for 0.99, among them is Midnight by J.K Beck aka Julie Kenner, The Lies of Locke Lamora by Scott Lynch ( which I have featured before.)
For a longer list, with covers and links check out SF Signal’s round up.