I'll Be Gone in the Dark by Michelle McNamara (2018)

Subtitled: One Woman's Obsessive Search for the Golden State Killer. 

McNamara, who passed away a few years ago at age 46 and was married to Patton Oswalt, was obsessed with her DIY search to find the identity of the East Area Rapist in California. Very absorbing until the very end, where her assistants tried to piece together the remainder of her search after her death. She was a terrific writer, and it's a chilling story. Perfect for the myriad fans of true crime podcasts and amateur sleuthing.