Does anyone here subscribe to Kindle Unlimited? If so, do you use it enough to make it worth the cost? I don't know anything about it. I've just started downloading some free books to read, and keep running across Kindle Unlimited, so am curious. I don't have a dedicated reader, just the Kindle app, and I mainly use that when I e-borrow books from the library, but I might be interested in it in the future if it's a good value. Is every title included, or is it like Prime, where only certain titles/authors are included?