So says Blake Snyder in his wonderful book, Save The Cat - The Last Book On Screenwriting That You’ll Ever Need. What he says would apply to books too.
He says every great movie has a logline, one sentence that tells you what it is! He gives examples and says that the best has four key characteristics. Examples:
A newly married couple must spend Christmas Day at each of their four divorced parents homes - 4 Christmases
A just hired employee goes on a company weekend and soon discovers someone is trying to kill him - The Retreat
A risk-averse teacher plans on marrying his dream girl but must first accompany his overprotective future brother-in-law - a cop - on a ride coming from hell! - Ride Along.
A cop comes to LA to visit his estranged wife and her office building is taken over by terrorists. - Die Hard.
This is broadly true of book publishing too, especially non-fiction, if you watch sales rep selling a list of forthcoming titles to a buyer in a bookstore, they probably get only a minute, maximum, to show a book cover and describe it. Hence the cliché in the business that if you can't describe it in a minute it's a dead duck.
He says the four basic elements of a logline are:
1. Irony. It must be in some way ironic and emotionally involving - a dramatic situation that is like an itch you have to scratch.
2. A compelling mental picture. It must bloom in your mind when you hear it. A whole movie must be implied, often including a time frame.
3. Audience and cost. It must demarcate the tone, the target audience, and the sense of cost, so buyers will know if it can make a profit.
4 A killer title. The one-two punch of a good logline must include a great title, one that “says what it is” and does so in a clever way.
This is quite a tough discipline, I have always been lousy at titles and point 4 blows my present one out of the water - And The Fire And The Rose Are One.
What about: A man thinks he met the living God in New York City, but She chose Him and takes him. - God Alive in New York City.