It’s tricky, I haven’t seen your work or theirs to compare it, but employing the same structure as another writer is not plagiarism in my opinion. There are set structures that just work in writing, whether for books or articles. Just like there are set structures that work in movies. How many rom-coms have almost identical structures! I wouldn’t acknowledge the structural influence for your book as long as your content is completely different. That’s just my personal opinion.