Hi Neil,
I think that like Amazon, Smashwords will only allow reviews from people who have made a purchase -- any purchase through the site. At Amazon I satisfied this requirement by downloading an mp3. If I might suggest,
go to my profile on Smashwords and pay a quarter or whatever for one of my listings. Hell, pay a penny, the cost isn't the point. My hunch is you'll then be able to post the review for *Risen* or for any titles on Smashwords. And if that doesn't work, I'll email Mark Coker at Smashwords. Doesn't make sense to me to restrict who can review when so many titles on Smashwords are free (or pay you *want*). But I can understand that a certain level of integrity has to be maintained; otherwise, any troll could go in and blast authors without even reading their work. Best of luck! -JMD