...by which I mean the end of Éowyn, Book 1: The Cage. In terms of publication I'd guess about nine more chapters, but at the original writing everything from Chapter 24 onward was one very, very, very long chapter; one which I've decided to split up into more digestible parts.
I felt it for the best, as the content of these final chapters isn't going to be particularly easy to digest. The content warnings in the headnotes are to be taken seriously; the book ends in an extremely harsh and decidedly unpleasant fashion for the title character.
Knowing what "happened" in these chapters is necessary to understand a lot of what Éowyn will struggle with in Book 2. But I certainly understand if some readers feel the need to step away before the end of Book 1. Sometime after I've published the final chapter of Book 1 I'll write a recap of the essentials here in the blog, just so no one needs to be completely lost when Book 2 begins.
For those already unsure what's going on (though I feel the introduction makes it fairly obvious), there's a clue/Easter egg in Chapter 25 that will give it away for readers familiar with Tolkien's posthumously published writing. Everyone else could just use Google if and when they see it, but to be honest I think it's more rewarding to wait for the reveal in the final chapter. And if that still doesn't make it clear, the Easter egg itself will be explained in the first chapter of the next book.