Cold Days: A Novel of the Dresden Files is a fantasy novel by American author Jim Butcher. At 515 pages, it is the longest installment of the Dresden Files series to date, and takes Dresden from his coma in Arctis Tor to the fulfillment of his responsibility as Winter Knight.

In this 14th book of the series, wizard Harry Dresden must face his biggest battle yet, and learn the full scope of his place in the universe. He might prefer not to be the Winter Knight, but it has saved his life and he has a role to fill, whether he likes it or not.

For a significant period of time, Dresden has been absent from the mortal world. And the people he loves have gone on. Some of them have found love. Others have grown stronger and learned to survive without him. They haven't exactly been happy, and they have missed him, but they have lived their lives, fighting still against the forces of darkness arrayed against them in his absence.

Dresden finds that all is not what it seems to be in the dichotomy between Light and Darkness, Summer and Winter. Summer powers can be just as deadly as those of Winter. Rules can be broken, and consequences will be had from that breakage. Everyone has a mantle to bear, and struggling with the consequences of power is part of that battle.

Dresden has more power than he ever has. He has his mature wizardly power, but he also has been given the power of Winter. He fears turning into a monster, destroying his long-held moral code along with it. It is only his free will and his desire to stay true to his ethics that keep him from falling off the abyss. Everyone who cares about him must decide if he is capable of holding on, keeping the monster at bay. No one knows for sure if he is capable of doing so, even himself.

In the course of the novel, Dresden journeys back from death, and must face the people he left behind. He has to learn to trust those who have earned it, and to face his own fears. He also has to fully accept his own abilities, realizing his full potential. He finds that he can fight the grimmest, most powerful forces in the universe and outside it.