There are no words. This is probably the most powerful, the most harrowing book that I have ever read.
I thought perhaps I shouldn't write anything here. But then I read Elie Wiesel's Nobel acceptance speech at the end of the book:

I remember: it happened yesterday, or eternities ago. A young Jewish boy discovered the Kingdom of Night. I remember his bewilderment, I remember his anguish. It all happened so fast. The ghetto. The deportation. The sealed cattle car. The fiery altar upon which the history of our people and the future of mankind were meant to be sacrificed.
I remember he asked his father, 'Can this be true? This is the twentieth century, not the Middle Ages. Who would allow such crimes to be committed? How could the world remain silent?'
And now the boy is turning to me. 'Tell me,' he asks, 'what have you done with my future, what have you done with your life?' And I tell him that I have tried. That I have tried to keep memory alive, that I have tried to fight those who would forget. Because if we forget, we are guilty, we are accomplices.