The page https://www.amazon.com/best-sellers-books/zgbs/books/
looks to have been updated such that XPathItemLinks should be getting the div element with class 'a-column a-span12 a-text-center _p13n-zg-list-grid-desktop_style_grid-column__2hIsc' instead of getting the li element with class 'zg-item-immersion'.
There might be other changes, but I didn't see them.