Murder to Scale by Debra B Schiff

Model train enthusiast Tom McCloud is eager to assemble his portion of the annual Christmas train display in a local church basement. Instead, he discovers the bludgeoned body of a fellow modeler, Bill Murphy. Everything points to Bill as the hapless victim of a burglary gone wrong. With Bill's scratch-built locomotive missing, Tom is convinced the murderer had to have been a modeler who knew the true value of the stolen engine. In the course of tracking clues that lead to other hobbyists and their elaborate train layouts, Tom unearths surprising secrets lying behind the placid facade of small-town Pennsville. Can he discover the truth before his investigation is derailed and he becomes the next victim of a ruthless killer.