When you have to use the word "about" to describe your idea--for a book, film or story--you are in trouble.
On page 28 of his excellent book on how to write nonfiction, "Follow the Story," James B. Stewart describes the difference between a topic and an idea:
"...a topic is not an idea. I have had to make this point to students and writers on countless occasions. Topics are inherently boring, because they pose no questions and incite no curiosity. They are like encyclopedia entries; interesting only if it happens to be what you want to look up. "Women in law" is a topic. "Welfare cheats" is a topic. "South Africa" is a topic. Reporters would come to me with the most earnest demeanors and say something like "I want to do a story about how oil companies are causing explosions at natural gas facilities." When I stifled a yawn, their outrage would be apparent: "How can you not care about something so important?" The answer was simple: anytime someone had to use the word "about" I knew we were discussing a topic, not a story. I would urge the reporter to come back with something more specific: What company? What explosion? Some topics are more interesting than others, but they should never be mistaken for ideas."