Six Floors to the Top by Karma Kingsley

Ellen Carp is inches away from being the youngest managing partner ever at her firm. At 29, she’s done nothing but stay laser-focused on her goals. The only thing standing in her way is Arieon Banks. He’s just as arrogant as he is useless, but he’s got nepotism on his side. Being the boss’s nephew, he proves to be a real challenge to Ellen’s promotion. But, when Ellen and Arieon get stuck in an elevator together, she learns he can be a real challenge in other ways too.