The Idea Factory - The Missing Serial Killer
The book starts out in a police station. There's a task force surrounding a recent string of deaths that are tied to a serial killer. They receive a new message from the person claiming responsibility, a puzzle on who the next victim is and when they will be killed. They've gotten similar messages before, but never solve the puzzle in time to save them. They're up all night trying to solve this one, figuring it out a good three hours after when the person is supposed to be dead. Still, they rush out, trying to find them. One team goes to where the message said the body would be found, while another team goes to where the victim lives, making sure that no one else was killed in the process of taking the victim (which happened on a previous murder). Only the victim is still in their bed, yelling at them for waking them up.
At first, the police is wondering if they solved the clue wrong. But when there are no other reports of dead bodies that match the clue, they're left scratching their heads, wondering if the letter was from a copy cat or if something happened to the serial killer.
Cut to the serial killer himself, and he's doing something monotonous as part of his normal life. Something came up, an unexpected visit from a relative or they forgot about a thing with their kids. The book continues with them in their everyday life, but with the police chasing him down. Because he messed up the clue, they're getting closer to his identity.