Unlike many other large subreddits r/books has not made any statements about the API changes. I did try and post something about it but it ended up getting deleted. At 22.1 million users this would be a pretty significant addition to the protest.
Does anyone know why there hasn't been anything official?
My general feeling is that the only reason to delete a thread is if it's spam or somehow offensive to site wide rules against violence, racism, etc.
Deleting a thread because you don't like it or it's inconvenient is a mark of cowardace and cowards have no business being mods.