That's not how it usually works, does it with Microsoft? It would be very limiting and annoying to be unable to read books without internet access (say on the beach on holidays, for example). Certainly not the case on Kindle.
There were cases were people's Amazon accounts were cancelled, so they couldn't buy new books from Amazon. The books they already bought remained on their kindles, though.
There were also cases of Amazon deleting books from kindles, when the books became illegal.
Any reason to assume Microsoft operated in a very different way?
If I had bought all my books on Microsoft, I'd be very happy right now. I would be getting hundreds or even thousands of dollars back, that I could use to buy new books.
Won't the books remain on the reader device, even if the store closes?
The discussion is also old. I realized that I end up lending only a small fraction of books to other people, and my kids will probably not care about most of my books. Storage of paper books also costs money, so rebuying the few books I want to pass on or reread may be cheaper than buying and keeping physical copies of books. So I chose ebooks.
There were cases were people's Amazon accounts were cancelled, so they couldn't buy new books from Amazon. The books they already bought remained on their kindles, though.
There were also cases of Amazon deleting books from kindles, when the books became illegal.
Any reason to assume Microsoft operated in a very different way?