It's Not the Length of the Headline, It's the Strength That Counts
In the foreword to the previous edition, David Ogilvy wrote: "[John Caples] taught me most of what I know about writing advertisements. For example:
1. The key to success (maximum sales per dollar) lies in perpetual testing of all the variables.
2. What you say is more important than how you say it.
3. The headline is the most important element in most advertisements.
4. The most effective headlines appeal to the reader's self-interest or give news.
5. Long headlines that say something are more effective than short headlines that say nothing.
6. Specifics are more believable than generalities.
7. Long copy sells more than short copy."
I learned most of what I know about copy writing from those who'd been taught by Caples, though I didn't realize it until I edited his book! It's not too late for the current generation to stop writing long enough to read it and learn a bit more, too.