How to write an “Elevator Pitch” of your book.
Being able to describe your novel in one sentence is a useful skill. It is called an “Elevator Pitch” because the idea is one could speak to an agent or publisher while riding an elevator and quickly tell them what one’s book is about.
Note to readers: Never actually do that! Agents spend a lot of time slogging through slush piles, they do not want you pitching your project in an elevator, a restroom, or other non-professional space. They just want to pee in peace. Really.

“Maybe if I pee in this cornfield they won’t be able to find me.” -agent who has been ninja-engaged one too many times.
That said, if an agent or publisher is met in such a space and they ask you for the information, (They. Ask. You.) then this is what they want to hear. They want a concise and interesting sentence about your book, not a verbally upchucked complete re-telling of the entire story.
Think of an elevator pitch as an old-fashioned calling card. Back in the day, people would visit others and leave them a calling card with their name on it if someone was out. That would let the absent person know you stopped by. Your elevator pitch is the same. Short and sweet, it should entice the agent, and they will then decide if they want to know more.

This melon does not require a great deal of description. “Butt melon” pretty much covers it.
That one line description is useful for other things as well. Twitter has regularly scheduled events where people tweet short “Twitter Pitches” and quite a few agents take a look at them. They are also useful sentences to put on a bookmark or online banner to get the word out about your project.
Made famous by his silly show that made the formerly Hedgerow Players a household name when no one had ever heard of it, a young actor and wombat named Stevie is surprisingly given the chance to head the new playhouse, along with the responsibility of making its debut show a raging success, despite the fact that actors from the old theatre, both young and old, threaten to make the new venture fail in their jealousy.
That, my dear readers, is a reasonable facsimile of a one sentence pitch I just read over at the National Novel Writers Month (NaNoWriMo) website. I’ve changed the hell out of it because writing one sentence pitches is hard, and I’m not trying to shame anyone here. Read that example again. Can you imagine that on a bookmark? On a banner? Could you make any sense of that if you heard it while you were peeing? Can you even tweet that? I don’t think so. Despite the fact that it is technically one run-on sentence, it’s far too long and there’s way too much information in there. Too much information makes it confusing and boring.

I can’t even shove half of that onto a banner.
I read many writer’s one line pitches over the last few days and there are two things I noted in many of them. Too long and a lack of engaging language. The point of a one line pitch is to describe the feel of the book, not to try to tell the entire story. Try to condense your plot into one sentence and you’ll end up with one of these leviathans. Yes, there are many tricks to write crazy long sentences, just ask Dickens, but the idea of the elevator pitch is NOT to make the longest sentence humanly possible. You people are fooling no one!
So, what do you do? My advice is that you aim for the following things:
–Make it short. The pitches that are getting the most positive attention over at NaNoWriMo are the short and sweet ones. Ditch unneeded information. In the above example, we don’t need to know what the old theatre was called, for example. Too many details will kill the pitch. If you have more than a couple clauses hooked together, it’s too long. ( <— two clauses!)
– Use engaging language. I don’t mean big words, I mean make it interesting. Dry language will make a dry pitch.
– Use the voice of your MC, when possible. At the least, make it about the MC, not exposition or world-building. This is especially a problem for speculative fiction. You can’t explain the entire world of your book in one sentence, so don’t try. Find a word or two that lets the reader know if it’s futuristic, or fantasy, or sci-fi. That’s really all you need.
I made a one sentence pitch for my NaNo project. Is it amazeballs awesomesauce? No, I’m sure it isn’t, but it’s not bad.
Nick has to save people every damn day.
That’s it. That’s enough. We know that Nick has to save people, and we get the idea that he’s sick of it. We’re left wondering why he has to save people, and why he isn’t happier about it. Those “whys” and that wondering is what might get you a request for further information on your book. Remember, it’s a calling card. It’s only purpose is to solicit a request for more information, not describe your entire book.
And look, it fits on a banner.

The banner came before the pitch. It’s a great way to force yourself to be concise.
Consider your options. Cut unnecessary world explanation. Design a banner or a bookmark and throw it on there to see how it looks. There are free programs online if you aren’t the artistic type. Try to instigate curiosity about your project instead of explaining your project.
I wish you luck with it, because it isn’t easy, but it’s totally doable.

On a side note: it’s almost Halloween!