The official Spiderweb Software website points us to both a review of Avadon: The Black Fortress and an interview with Spiderweb's Jeff Vogel that have surfaced at a website called All Your Lives. In the latter, Mr. Vogel covers his company's history, his favorite RPGs, the success they've enjoyed with Avadon, and more:
RyJek: Did you ever consider taking what you have and let's say turning Avadon into an MMORPG?
J.Vogel: No. Doing multiplayer stuff is hugely time-consuming and demanding, and all it would do is distract us from what we're really good at. I'm not ashamed of sriting single-player games. Single-player games are awesome, and there are lots of people who still love them.
RyJek: What is your best selling title and what number of copies are we roughly speaking of?
J.Vogel: At this point, it is Avadon: The Black Fortress. On Steam, on iPad, on our site, it's been an enormous success for us. Far beyond anything I dreamed of when I was writing it.