The Best Book on Screenwriting?

I hadn’t heard of Lajos Egri until a classmate’s roommate’s dog (whom the roommate refused to neuter, I might add) tore to shreds my copy of Joseph Campbell’s The Hero With a Thousand Faces, which I lent to said classmate over the weekend. It was the only required book in my undergraduate screenwriting class. But instead of buying me a new copy (a norma…