This question is one of the hardest questions for me to answer. For a couple of reasons:
1) I feel like the biggest nerd when I talk about my novels--Confessions of an Immortal heart deals with an immortal girl (woman?), most people chuckle and say "Not another Twilight". Don't worry, it's not. When I actually say what it's about, they're usually a little more interested:
(This is my query letter)
Shakespeare's Romeo and Juliet tells the story of a love so intense, the two youths commit suicide rather than facing the rest of their lives without each other. In Twilight, Edward thinks Bella has died and chooses to end his existence rather than spend eternity without her. Both stories give the ideal ending in that both lovers are together again. But what happens when one half of the equation is permanently missing? Can true love really last forever, or will holding on just destroy you?
In Confessions of an Immortal Heart, the reader finds that the love interest has been murdered and all the narrator wants, is to die as well. However, due to some defect she can't figure out, she doesn't get hurt and she just won't die. The story revolves around the immortal narrator's inability to cope with her loss, lamenting all the times she should have stepped in to save her mortal's life. Each chapter gives insight to the development of their life together; when she comes home to find a him standing before her, her trying to kill him, their first kiss, the time he arrives after being attacked, up to the 'accident' that claims his life, and then her living in the Godforsaken world without him. The lack of names plays into the ending of Confessions of an Immortal Heart, because without him she's lost her identity.
Then...Igniting a Firestarter...
Deals with different covens and things like that, so I feel like a geek again. But it's cool because it's relate-able to real people, and people I've met every day....just exaggerated :) (I'm not posting this query letter because it doesn't quite rock yet).
2) It's hard to sum up your (my) entire novel in like 2 seconds and make it sound like it's the best thing since sliced bread. I've noticed if I talk too long people's eyes start to glaze over and I try to talk faster to say "But oh no!! They're in love, and it's an awesome story!!" Firstly, it is an awesome story (or so I think). Secondly, I need to get to the point already.
Outside of that...
I need to start preparing for the PNWA conference (which...I got my card in the mail yesterday confirming the fact I am a member :) ). But, there will be rapid fire rounds (I have 3 minutes to talk about either novel)...and I need to talk fast and coherently.
Even at first a query letter is hard because I'm too involved with the sub plots and while I think they're important the person reading about them...may not.
The writing life is hard....:)