You Know Who Killed Me — Loren D. Estleman

Amos Walker is at low ebb. Just released from a rehab clinic, the Detroit private detective has to marshal his energies to help solve a murder in Iroquois Heights, his least favorite town.

The area is flooded with billboards rented by the widow of Donald Gates, an ordinary suburbanite found shot to death in his basement on New Year's Eve: "YOU KNOW WHO KILLED ME!" they read, above the number for the sheriff's tip line. Complicating matters is a ten-thousand-dollar reward for information leading to the arrest and conviction of the murderer, offered by an anonymous donor through the dead man's place of worship.

Initially hired by the sheriff's department to run down anonymous tips, Walker investigates further. The trail leads to Yuri Yako, a Ukrainian mobster relocated to the area through the U.S. Marshals' Witness Protection Program.

Shadowed by government operatives, at odds with the sheriff, and struggling with addiction, Walker soldiers on, in spite of bodies piling up and the fact that almost everyone involved with the case is lying to him.