Yeah, I'm also not a big fan of ghostwriting in the domains where it's prevalent. For what it's worth, though, academic writing is very much not one of those domains: taking LLM's out of it, if ten years ago it had turned out that the "author" of a math textbook like this one had paid someone else to write the whole book for them, that would be considered major academic misconduct and that person's reputation would have been pretty severely damaged. I do think it makes sense to take the norms of a particular subset of the publishing world into account when thinking about what a reasonable reader expects when they see someone's name on a book.