Whew. Query letters, you are my bane!
Seriously. I NEVER felt that I was very good at them. I didn't use them on most of my novels, since I sent to places (like Tor) which didn't require them at the time. With my agent, however, I DID use them. Only the first one really mattered, since that hooked him into looking at some of my writing. Even though he passed on that book, from then on, I could simply send him a "Hey, you want to see the next one?" email, and he'd let me bypass the query stage.
I did ask him, later on, how one wrote good queries. Here are a few tips he gave me:
1) Don't make the plot sound like a movie trailer. Stay away from hypothetical questions, stay away from dramatic cliff-hanger sentences.
2) Do include a paragraph about yourself, but try to make the information in that paragraph relevant to your writing and the story.
3) Keep it to one page.
4) Try to include a sentence or two that hints how clever your book is.
So, I think the trick here is to NOT explain too much. There's a sweet spot for writing a query, one I'm not sure that I can do myself. You're right--if you boil the plot down, it will sound dumb. (Little furry-footed British guy needs to throw a ring in a volcano.) However, if you can write a paragraph that doesn't try to cover the whole book, but gives a good idea of what is unique about the story, maybe that would work.
Aaaanddd...just looked at my original query to Joshua. Ug. It stinks hardcore. You DON'T want to see it. The only reason I got looked at was because I'd met him at the Nebula Awards, and he'd agreed to let me send the first three chapters along. The query stank, but my writing--fortunately--was good enough that he was willing to look at something else by me.
