The good people at COPIM, in their formal announcement of the Open Book Collective:

OBC will act as a collector of revenues accrued for new membership packages from institutions – primarily academic libraries – with this revenue then passed on to OA book publishers and infrastructure providers. A portion of the revenue will be retained to cover the platform’s administrative overhead costs.

The Open Book Collective, when it’s launched in the spring, will help solve the APC/BPC author-exclusion problem, by directly linking funders to publishers (and infrastructure stewards). I see the OBC as the book counterpart to the journal-centric OACIP from LYRASIS. They are—in practice, in OACIP’s case, and in active development, now, for OBC—the two main examples of the mission-aligned funding exchange.