*400 Days* by Chetan Bhagat is a thriller novel that delves into the complexities of relationships, secrets, and human emotions. The story follows the lives of several characters who are interconnected through a central mystery that unfolds over a period of 400 days. The novel combines elements of suspense and drama, exploring themes of trust, betrayal, and personal growth. It offers a gripping narrative that keeps readers engaged as the characters’ secrets and motivations are gradually revealed.