What is it with subject lines?
Either you think they're stupid and thus don't use them, or you think they are somehow the source of all good and, if you stuff as many words in as possible, one of them will sprout an offer of representation.
Knock it off!
The subject line is how my email is sorted. And I utilize THE dimmest sorter on the planet: my mail management software.
Sadly, MMS does EXACTLY what I tell her, with zero imagination, intuition or ability to integrate information. Working in your favor however is that dear old MMS doesn't get anywhere near as impatient or crabby as I do.
So, let's review:
GOOD: Query for (TITLE OF YOUR BOOK HERE)
BETTER: Query for (TITLE OF YOUR BOOK HERE) a novel OR non-fiction
BEST: Query for (TITLE OF YOUR BOOK HERE) a novel OR non-fiction/category
Bad: Query for TITLE (and by this I mean you simply write title. yes I've seen it)
Bad: RE: Query for...
(the problem here is using RE: That makes me think it's a reply to a query or an ongoing conversation. Because the RE comes first, MMS does not recognize it as an initial query.)
Bad: Query for your consideration
Bad: "Query" (the quote marks confuse MMS)
Worse: Query for "Title" by "Author" with "enticements"
Worst: Drinks tonight?
Get the idea?
Simple works best.
I really notice this when I come back from a long weekend without mail access and I have 479 emails piled up. I sort by subject line and there are always 20 or so people who just can't quite figure out what to do with the subject line.
I make a very serious effort to get my queries handled in a timely manner. If your query isn't recognized by the MMS it just sits there till I get around to it. Since you're not a client or an editor, or any of the other people I know, it can sit for a long long time.