I know the "gimmick query" is a bad idea, which in theory renders the rest of my question unnecessary. However, there is the occasional non-formulaic query that is exceptionally effective, as in the case of Josin McQuein's query for Premeditated.
The novel I'll be querying is an urban fantasy rewrite of a Greek myth, and as I've wrestled with the query, it occurred to me that it could be really fun to write it as an invocation of the Muse. I obviously don't want to burn bridges before I build any by querying agents with a gimmick that just won't work, no matter how clever I may think I am. I'd love to hear your thoughts on this.
You're conflating "gimmick" and "non-formulaic" to come up with what we like to call a rationalization. And you know this cause you're asking if it's ok.
Josin McQuein's query on QueryShark was NOT a gimmick. It was exactly what you want a query letter to be: enticing.
If you can write an invocation to the muse that is enticing, more power to you.
I STRONGLY urge you to rethink this. When you look at Josin's query you see that all the plain ordinary fundamentals are there: name of the protagonist, name of the antagonist, what choice the main character has to make, or is making. It starts at the right place: the fork in the road. We have a sense of urgency and tension.
All those are the fundamentals of a good query. That she wrote it in short sharp sentences that lend themselves to a poem is just amazing style. You can be stylish in your query, you can't be gimmicky. Knowing the difference isn't a piece of cake but the more you read flap copy, the more you'll be able to evaluate what works and what doesn't. (Flap copy is the description of the book on the front flap of the book)