The Road to Finding Us by Kat Singleton

Lily Morrison was as guarded as a woman could get—until Aspen Bellevue came along during her first year of college. His playful banter and sexy smirk paved a way straight to her heart. But that was before his playboy tendencies demolished it. After being hurt by the one man she ever truly wanted, she swore she’d never let herself fall for him again.
Aspen always knew his best friend’s twin sister was off limits. Lily was the one girl he couldn’t have—and yet, the only one he pined for. But by the time he realized this, ready to change his ways, it was already too late.

To her, Aspen will always be a womanizer. To him, she’s a sassy spitfire whose feathers he still loves to ruffle.
Now, after a few years apart, they’re thrown together to reunite with their old college crew. But this time, Aspen has a plan. He wants Lily to be his by the time they travel from Texas to South Carolina. Meanwhile, Lily wants their baggage to stay in the past—where to her, it belongs.
How much could go wrong when two sworn enemies—with two different outlooks and renewed sexual tension—come together in a car for a week-long road trip?

Only one of them wants to find out.