A Vow of Hate by Lylah James

The story revolves around Julian Brandon and Mila. Julian is a powerful, cold, and ruthless man who was deeply in love with a woman named Aria. When Aria tragically dies in an accident, Julian places the blame entirely on her sweet, identical twin sister, Mila.

Before her death, Aria was arranged to marry Julian to secure a massive merger between their wealthy families. Driven by a dark desire to punish the woman he holds responsible for his heartbreak, Julian forces Mila to take her dead sister's place at the altar. Mila, trapped by family obligations and her own crushing guilt over the accident, agrees to the arrangement. Julian vows to make her life a living hell, turning their marriage into a psychological battlefield of resentment and unspoken attraction.