Joona Linna is the kind of fictional detective who grows on you — quickly. Self-assured and whip smart, he has a quiet personality that masks a stubbornness and arrogance he uses to bull through situations that deter fainter colleagues. And so far in this exciting new series from Sweden he is only lightly tormented by the predictable internal demons that so many mystery writers wield like riding crops to torment their detectives. More on that later.

In “The Hypnotist,’’ Lars Kepler’s first book, Linna shared top billing with a second character. Now in “The Nightmare,’’ the second Kepler book to hit the States, the narrative is all his, and he flowers in all his freakish glory. He is something of a Clues Whisperer, sensing the presence of information hiding in the periphery; at one crime scene he detects a near invisible footprint on a wall that his police technicians had missed.