Asimov is a prolific writer. He wrote hundreds of true science papers. This work is from the days when Science Fiction was written by scientists. If you have not already enjoyed this work I would suggest it strongly. I read it the first time about 35 years ago and I still enjoyed it again for the 20th time.. I read a few books a week, not many do I read over and over again, but Asimov's work is that enjoyable.