All's Fair in Love and Pickleball by Kate Spencer

In this sweet and steamy romcom by the author of In a New York Minute, two rival pickleball players find themselves faking a romance—until they start falling for each other for real.
 
Bex Martin’s racquet club is her entire world. But the business she inherited from her mother has started to feel more like a sinking ship. That is, until Nikolaus Karras—a former tennis bad-boy with an ego as big as his serve—makes himself at home on her courts.
 
Niko has something to prove, and a high-stakes pickleball tournament is just what he needs to get back in the game after a career-ending injury. When he is finally able to set his ego aside to ask for Bex’s help, everyone assumes that they are a couple—on and off the court.
 
But she needs the prize money to save the club, and he needs a win to restore his reputation. So now they have a fake relationship as well as a doubles partner that they can’t seem to resist. Game on!