The Horses of the Night — Michael Cadnum

San Francisco architect Stratton Fields has just discovered that a contest was rigged against him and that the man who engineered the cheat, Ty DeVere, is determined to keep Stratton from success. But when Stratton's enemies, including Ty, start dying mysteriously -- and Stratton encounters several apparitions -- he wonders if he unknowingly made a deal with a supernatural force. Or maybe he murdered these people himself and has no memory of his deeds. Stratton must confront both the humans and the spirits who are causing mayhem to discover the destructive truth.