Today I finished Techniques of a Selling Writer by Dwight V. Swain. (1965)
I bought and read the book because I was intrigued by Motivation-Response-Units mentioned by blogger Randy Ingermanson in his blog Advanced Fiction Writing. A concept which Ingermanson credited to Swain.
If a how-to-write book written in 1965 is still in print, it has something useful to say.
This book does in spades. Ninety percent of my copy's pages are highlighted, underlined, or both. I give it four stars.