"Less money into books -> less books" seems like "demand goes down -> supply goes down" and fits my unsophisticated understanding of economics. It's not necessarily clear that reduced copyright -> less money into books.

Authors have managed to produce novels while holding down demanding full time jobs (or in at least one bestsellers case, still in full time education) at the same time. It is not necessarily the case that the only way books get made is full time writing.

You could also argue that the reduction in books from reduced copyright would be balanced by an increase in currently unwriteable "remixes" of existing works. Copyright could be, for example, the only thing holding back an explosion of people making enough to live on publishing fan-fiction. Who speaks for them?

There's still scope for a sweeping reduction, in the States at least. Reducing the duration from "Year of Authors death + 70 years" down to, just "Authors death", for example, clearly couldn't lead to any given author producing fewer books.

I absolutely agree that if there is a forum on the scope and duration of IP, small-money authors should be represented. It doesn't seem like that will be happening any time soon though.