I'm looking for a story that was written like a report concerning two scientists studying the dead civilization of Earth. They did this by re-animating dust and bones and asking the formerly dead person what happened. They had little success until the last being they re-animated said "We made a mistake. I can fix this. Everything will be fine." Apparently he did. We also learned that the scientists were aliens.
It sounds a bit like The Monster/Resurrection by A. E. Van Vogt, though I think this was written well before 1968.
I lost the book before I was able to finish it, so it may fit your description. It had some interesting observations concerning life as we know it. I have been unable to find the book since my loss. I hope you have better luck.