[peterarmstrong]

That's a really good feature; we'll add this to our queue. Thanks!

[StavrosK]

I'll second that. I think a post-pay model is really useful. The only problem is getting people to come back to pay for the thing.

[pgeorgi]

Combine it with other features (Write the author, discuss the book with author and readers, rate the book) and invite the reader on the last page of the book.