Query Letters--Level of Detail

Here's another good quote from Miss Snark from a post on her blog:

Detail is the devil in query letters. You can't go into much, but broad generalizations are boring. You have to find one or two compelling details that really entice a reader. Try not to panic though. Even if your query letter truly sux (9 out of 10 do), if your pages are good, you're still in the game.