Nice list so far...

I would add:

"2.239 Tested Secrets for Direct Marketing Success"
"Method Marketing"
and "Million Dollar Mailings" all by Denny Hatch.


If you wanted to go beyond copywriting to direct marketing and marketing I would add:

"$12 Billion Of Inside Marketing Secrets" by Steven Dworman
"7 Steps to Freedom" by Ben Suarez
"The Republic of Tea" by Mel Ziegler, Patricia Ziegler and Bill Rosenzweig
"Being Direct" by Lester Wunderman
"Marketing Secrets of a Mail Order Maverick" by Joe Sugarman
"The Complete Mail List Handbook" by Ed Burnett
"Infiltration Marketing" by Don Debelak
Any of the "Wizard" books by Roy H. Williams
"Peterman Rides Again" by John Peterman

Some flat out terrific business books that have influenced me greatly are:

"Winning Through Intimidation" by Robert Ringer
"The 80/20 Principle" by Richard Koch... his "The Natural Laws of Business" is also great.

And I can't forget the late great Peter Druckers, "Innovation and Entrepreneurship"... just a fantastic book.