All very thought provoking stories. Some of them took me a while to get my mind around, but I did enjoy every word of this book. "Missile Gap" is a particular mind-blower, with the Earth somehow being transported to a flattened disk, outside the Milky Way and in the far future. "A Colder War" has inspired me to put Lovecraft on my "to read" list. I think my favorite was the last, "Palimpsest." A palimpsest is a scroll or book that has had the text scraped off so that it can be reused. In the context of this story, it refers to time travel, going back again and again, trying to fix an event in the past that went wrong. A time travel agency is trying to save humanity from extinction by reseeding Earth with populations from earlier epochs.