The Final Friends Trilogy.
This omnibus collects Christopher Pike's Final Friends trilogy - The Party, The Dance, and The Graduation - a young-adult mystery following a group of high-school friends after a girl is gravely hurt at a party. Across the three books the characters chase who was responsible while navigating romance, jealousy, and secrets, building to a reveal by graduation. Pike writes in the fast, suspenseful style that made him a staple of teen thrillers in the late 1980s and 1990s. For nostalgic readers it is a bingeable whodunit gathered into one volume.