Duking It Out — EJ Russell

The first book in Royal Powers Season I got me hooked on writing in this world in the first place and has Royal dukes from rival countries, shipwrecked on a deserted island.

Enemies to lovers, opposites attract, superhero rom-com, featuring Only One Bed, a grumpy duke who should know better than to jump to conclusions, a self-doubting duke who's good with his hands (heh), gossipy seagulls, competent assistants, a guaranteed HEA, and (unfortunately) capes.