I am not currently involved with Kindle Unlimited, which means I know very little apart from what you know: it’s a loaning service, it appears to be opt in, and it allows people to read books without purchasing them. Which sounds, to me, a lot like this thing called “the library,” which saved my life as a child.
I love libraries. I love libraries. Libraries are how you play your career as a long con, because that teenager who can’t afford to buy my work now, but puts a hold on it the second it enters the library system, is the future adult who will buy everything I write. And sure, some people may read a book, decide I’m not for them, and not become fans, but they would have done that anyway. I would rather people have access to books than get paid for every set of eyes that crosses the page. (Note that this is not an endorsement of illegal downloads: libraries are a legal and legit way to read things, and they are awesome, and they do pay authors on a copy by copy basis, if not on a reader by reader basis.)
Kindle Unlimited strikes me as Amazon trying to pretend that they invented libraries and that libraries should always have a payment model attached, and that makes me sort of uncomfortable. At the same time, I recognize that many indy authors don’t have a shot at library representation, so I can see the value. I’m just a little uneasy about what this will mean for the digital divide.