They can be useful to attend as part of the audience, but having a stall is even more valuable. (littletechgirl.com)
That may mean cutting out long words and using shorter, simpler ones (especially if there's a large part of your audience whose first language isn't English). (creativeboom.com)
I would imagine that it would be harder to release if a good part of your audience already «owns» the books, but apparently I'm wrong about that. (comicsworthreading.com)