The Nightmare (Joona Linna #2 ) by Lars Kepler

A drowned young woman is discovered on an abandoned pleasure boat drifting by the Stockholm archipelago—strangely, her clothes are dry. The next day in Stockholm, a man turns up dead, hanging from a lamp hook inside his completely bare apartment—but how could he have hung himself with no furniture to climb upon? As Detective Inspector Joona Linna begins to piece together the two mysteries, he discovers that they are a mere prelude to a dizzying and dangerous course of events.