You've got to have a good title for everything you write. I'm working on a title now for an article. So far I have the first part: "What Lorca Knew: ... " I'm very pleased with that but I need a subtitle after the colon. Having my complete title be "What Lorca Knew" would be rather provocative, though. I might opt for that. Titles should be brief and informative, prosodically effective. The scholarly convention most in favor now is to have an evocative phrase, often time a quote, followed by an informative subtitle that tell you what it's really about. The title "What Lorca Knew" is brief and both evocative and informative... but not quite informative enough perhaps.
There's a problem with having too great a title and then having the subject matter revealed in the subtitle be too mundane.