Gamow was a respected nuclear physicist and cosmologist who could write for the general reader. When this book appeared, the nuclear age had recently dawned but few scientists were writing about nuclear and other fields of physics so that they could be understood by the layman. Even more importantly, he could write in a way that stimulated the interest of young minds who were influenced to pursue their own careers in science, at a time when the U.S. seemed to be lagging the Soviet Union in the space race. It's hard to imagine now the fear and anxiety that Sputnik and later Yuri Gagarin's flight inspired, by beating us into space with both the first orbital satellite and first human space flight.
In the 40s and 50s there weren't many high level scientists or talented science writers writing for the general public like there were in succeeding decades. A few, like Martin Gardner, Lincoln Barnett (The Universe and Dr. Einstein), Lancelot Hogben (Mathematics for the Million, and Science for the Citizen), come to mind. And Asimov's wonderful books were still many years in the future. Since there was so little available, I even read the popular works of the eminent French astronomer Camille Flammarion who died in 1925.
So I treasured books like this and read all that I could find. Along with the Life Nature and Life Science Library, they kindled an interest in science that led to studying science in college and later a career. If you read the other reviews here you'll see similar comments. You can't say more for a book than that not only did it open your mind to the wonders of science but that it was truly life changing.