KindleUnlimited is a product that as a big reader I am interested in. But I do not think this is a product for everyone.
After a day of playing with it and exploring the titles here are a few thoughts. (Here is my updated thought after 3 months).
1) Unlimited, but only ten titles at a time. I have not seen official documentation of this, but on the Amazon message boards many people are reporting that there is a limit of 10 titles at a time. This is unlimited because you can check out as many titles a month as you want, but only 10 different titles at a time. Even as someone that likes to read several books at a time, a 10 book limit seems reasonable.
2) Do not miss the Audible Credits. In your welcome email there is a link about getting 3 free credits (one a month) from Audible. I thought that it was only for new Audible members so I did not click it initially. Later I learned that you have to click the link to get your free credits. If you are currently a member of Audible you get a credit added to your account the first month and one addition the next two months. If you are not a member, then you are being signed up for Audible and you need to quit Audible after three months. Audible credits can be used for any book at Audible, not just the KindleUnlimited books. The price of these credits, depending on your plan is $9.09 to $14.95. So signing up for three months of KindleUnlimited is like getting 3 credits for $6.66 each (two months of $9.99 and one month free).
3) No major publishers, sort of. Initially I thought HarperCollins must have been a part because several of CS Lewis’ books were included. But the ones includes are with Mariner Books. I found two of Thomas Merton’s books are included. Merton’s Seven Storey Mountain is a Houghton Miffin Harcourt book (as is the heavily publicized Lord of the Rings books). Houghton Miffin Harcourt is not a small publisher, but is not one of the big 5 and primarily focuses on textbooks.
Ebooks, especially of older books, are a gray area because they were not included in most publishing agreements so sometimes ebooks are self-published or have a different publisher even if the paper book is a regular publisher.
Open Road Media is a company that seems to specialize in larger name fiction and non-fiction that did not have ebook agreements and/or are out of print. And all of the Open Road Media books that I have looked for are included. So Dorothy Sayers, a number of Pat Conroy, older Susan Howatch, much of Octavia Butler, Pearl S Buck, John Jakes, some Michael Chabon, some Ann Patchett, etc. So if you like 20th Century Literary Fiction, you will find a number of books worth reading.
4) Is it worth it? Time had an article that suggested that if you read 16 books a year from KindleUnlimited, then it is worth it. That is based on $7.50 a book ($7.50 times 16 = $120). But I think that is too generous. Many of the books that are included are less than $7.50 to start with. And remember, this is rental not purchase. Personally, I think that you should based your cost effectiveness calculation amount at $3-4 a book. So you would need to read 30-40 books a year from KindleUnlimited to make sense. ($3 times 40 = $120 or $4 times 30 = $120)
However, I think it is better to think about this as a per month cost benefit. There is no reason that after the first 3 months (so you get your Audible benefit) you cannot stop, read some other things and then re-subscribe to KindleUnlimited later. ($4 times 3 books in a month is $12 which is more than the $9.99 cost)
5) Audiobook. Part of what makes KindleUnlimited different from Oyster or Scribd is the audiobook integration. Initially it looked like there were about 7000 books with audiobooks. But only about 2000 of those have free audiobooks. The rest have discounts on the audiobooks, but they are not free. I am sure I can find a few dozen or more audiobooks I want and for me that is worth the cost. I did have a problem with one book that was marked as having the audio, but it did not show up in the kindle iphone app. I contacted support and they suggested trying the iphone Audible app. And it was there.
6) Eink Ereaders – The main reason I did not continue with Oyster after my initial trial and review was that I primarily read on my Kindle. I believe that eink ereaders are far superior to reading on my iphone, ipad or computer (or android tablet if I had one of those). KindleUnlimited is the only one of the ebook subscription plans that has an option to read on an eink ereader as far as I can tell.
Summary: Basically, I think if you are a reader, especially if you like audiobooks and use Audible, you should at least get the one month trial. And probably pay for the first two months. After that, you should have a good idea if you are going to use it. But do not be afraid to cancel for a couple months, read something else and come back to it later.
Updated: I went through my fairly extensive Amazon wishlist (if you look at it on your eink kindle, it says whether the book is KindleUnlimited or not, but looking at the wishlist on a computer does not.) I moved my KindleUnlimited books to a separate wishlist and then added a few books that I ran across. Right now I have 62 books on the KindleUnlimited wishlist.
I also went through the Bookwi.se Reviews and found about 50 books that are in KindleUnlimited, roughly 1/3 (mostly public domain classics) have free audiobooks as well. I also tagged just the ones with Free Audiobooks if you are primarily interested in that.