I read through the article but it doesn’t seem to specify the nature of the book. How do we know it’s a “knock off”? It might very well be fanfiction. Copyright law aside, fanfiction can be original and is a valid artistic expression.

This is quite a nuanced issue. The author is claiming that the Rings of Power copied his ideas. Even if the author didn’t have the legal right to publish this book, he might have put original ideas into his work, and the Tolkien Estate should not automatically own these. The copyright owner “should” (within the current legal framework) be able to make you take down your derivative work, but they don’t own it. The article doesn’t specify why the original lawsuit was dismissed.