I've seen very good agents grab a manuscript from a single sentence more than once, but my favorite query consisted of two sentences that had a total of nine words. Two short sentences that said something brilliant in a wonderful way.
While slightly off topic, I know a top editor who grabbed a manuscript from an unsolicited query because the entire query consisted of five words. I'm the best there is. Turned out teh writer may have been exhaggerating a bit, but he was nonetheless very, very good, and the editor bought the novel.
I also know an editor who hired a staff writer because instead of sending clips, he sent just four words. I can flat write. Turned out he was underestimating his talent.
Not every agent or every editor likes the same old same old boring tell me all about your novel approach.
Frankly, an agent or editor who would rather read 2oo, or 250, or 300 words about a novel, rather than a few short sentences that show how good the writer is, wouldn't much interest me.
Really, don't you get tired of reading 250 words about this novel, and then 250 words about that novel? It takes about ten minutes for my eyes to blur, and for all of them to start sounding alike.
At this stage, I couldn't care less about plot, or about the chain of events that takes me from page one to page last. Any decent writer, and even a lot of lousy writers, can do this well.
A really good, talented writer will handle these things, so what I care about is finding writers who can flat write, who have something to say worth hearing, and who show me how good they are.
A decent to good writer can tell me all I need to know about a novel in a couple of hundred words. A really great writer, however, can show me how well they can write, and that they have something worth saying, in forty words or less. Often in one or two very short sentences. Given a choice, I'll take this writer each and every time.