Who is William Zinsser from On Writing Well and what is their importance?

William Zinsser is the author of the book. The subject of the book is largely about how the author writes, what brought him into writing, and what keeps him in the profession. He produces articles and nonfiction books, and so the focus is on these forms. The advice given is useful for all forms of writing, whether it be journalism, poetry, fiction, or business writing.