From SPARC Europe‘s summary of a recent gathering to discuss and inform the coming Plan S for books:

With almost 75 attendees, this workshop focused on business models for OA books and brought together experts from the field before ending with a document sprint. The sprint allowed the community to engage online by reacting to cases made by the presenters and providing other additions.

From the summary, it’s clear that a number of speakers—including Martin Eve, Agata Morka, and Koen Vermeir—warned against mimicking Plan S’s de facto crowning of APCs as the main OA funding model. One facet that wasn’t much raised, it seems, is the ripple effect on the rest of the world of any Plan S for books. The existing, article-level Plan S, because of its early movement and major funder buy-in, has (perhaps already) cast the die on APCs/read-and-publish not just for Europe, but for the rest of the world too.