That's Not My Name by Megan Lally

A dual first-person narrative, rotating between Mary and Drew. A teenage girl who wakes up on the side of a deserted road with no memory of who she is or how she got there. She is soon reunited with her father, Wayne, but without any memory of him or her childhood life. Drew, a teenage boy whose girlfriend, Lola, vanished without a trace, is the prime suspect in the disappearance and presumed murder. As Drew becomes more obsessed with finding Lola, Mary becomes more convinced that there is something off with her father. The novel provides more than enough breadcrumbs but cleverly counterbalances the breadcrumbs with logical counter-arguments, which keeps the reader guessing till the third act, when a number of blindsides drives the story to a fast-paced climax. 4/5