Deeply moving, highly involving and tense, this book is far more complex than it might appear at first glance. While appearing to be merely a science fiction novel, it deals with the impact of an obscene period of history on the souls of those who participated, as well as those whom time travel has gifted with the ability prevent it from ever happening. Despite the SF trappings, this is a very human novel, illustrating the terrible madness that overcame Germany during the war, as well as its lasting effect on humanity.
One reviewer has claimed Dunn "insults" through his use of "Christian trappings", betraying a lack of familiarity with the subject matter. Dunn makes use of Frank Tipler's "Omega Theory" to provide a platform for forgiveness and divinity that fits with the technological aspect of the future in the novel.
Dunn displays an astonishing grasp of emotion in "Days of Cain", moving the reader to tears at one moment, then despair, then rage, and finally joy and wonder. I've bought several copies of this book for friends (two of them Jewish), all of whom have later enthused about it.
A remarkable work by a truly gifted author.