After a certain amount of dithering and sample-reading, I used the coupon on
She Blinded Me with Science...Fiction, an f/m comedy romance set at a sci-fi convention with a Trekkie wedding held in Klingon in it which is reprinted and revised from another publisher, so it's probably been through the quality control editing phase twice.
I figured it was close enough to something I'd like to give a try and would actually read for more-or-less fun (and not just pure morbid curiosity), but far enough from what I'd normally pay to try during their regular coupon sales, that it would be the best use of the coupon, especially as the sample was vaguely promising but not immediately compelling. And the author doesn't seem to have any other books I'd be interested in that I might buy during a sale to check out if I liked her other works first so might as well use the freebie offer to pick up something in a purchasing vacuum.
Anyway, thanks again to the OP for sharing!