Dear Ana V….
Aim for a “relaxed professional” tone for your fiction query, which is more like flap copy than a letter to your banker. Strict formality is at odds with your project and does nothing to demonstrate that you can manipulate the language to tickle funny bones or spark wry smiles. You’re a professional of the creative arts, pitching to a professional who deals in creative products, so draft the query as a professional but then “relax” it with fresh, lively phrasing. Don’t go too far, though: wild wordplay and wackiness can easily overwhelm out of a fictional context.