Romance Thy Enemy (Love and Other Tropes #2) by Kayla McGrath

This is not one of her romance books, they’re not going to fall in love.

Mina and Graham have disliked each other for as long as they can remember, and everyone knows it. When asked to be the Maid of Honor and Best Man at their best friend's wedding, the bride and groom worry about making the two of them uncomfortable knowing the mutual disdain between them.

In an effort to alleviate any tension and awkwardness in the friend group, Mina fabricates a story that she and Graham have secretly been dating. What she can't understand though, is why Graham is so eager to play along.

Meanwhile, Graham has been slowly falling for Mina for years, but he hasn't wanted to make his feelings known—especially since hers have been crystal clear—but he wonders if their fake dating scheme could be his opportunity to make her fall for him too.

But soon, the lies and guilt begin to eat at them both and they have to decide if they'll come clean before the wedding, or keep up the ruse until their contract is due.