Dear Miss Snark:
I sent out maybe fifty queries on a novel about two years ago. No bites. I've since taken some writing courses and entirely rewritten it, though the basic plot and title, which I love, remain the same. When I send out queries now, with a totally different letter, might agents recognize it from before and not even read it? Would it be a good idea to change the title and even alter my name slightly so they don't recognize it as something they've already passed on?
If the only thing agents saw was a query letter, don't worry. Even Agent Elephant doesn't keep that kind of detail in his head, and I don't know anyone who tracks query letters. Fulls and partials, yes of course, but not queries.
If any of the agents read more than a query letter, tailor the query to tell them what you told me-it's faster, stronger, smarter with newly polished six million dollar shoes.
Agents understand that writers learn from experience and they retool and polish work that made the rounds a while back. This second query would not be an automatic pass, particularly with what you've told me: two years, writing course, reworking.
The resubmissions I'm not keen on are the "major revisions" that arrive too soon (less than three months) and don't mention any kind of outside help. Those get a cursory look. Yours I'd read.