Gary Halbert is a legend. He was one of the best and most famous copywriters who ever lived. His Gary Halbert Letter (which you can still access online to a great part) made him immortal. More importantly, Gary wasn’t only a great copywriter but he was also a great teacher. Someone who could simplify the concepts of writing winning ads and was willing to teach them.
Just read a few issues of his Gary Halbert Letter and you will learn more from it than from any blog post, book or course out there. Gary is probably responsible for introducing more people to the art of copywriting and direct mail than any other person before or after him.