Rachel Carson wrote about the harmful effect of pesticides on the environment and its effect on people and animals, particularly birds.
The title Silent Spring is meant to evoke an emotional response from readers when they consider that if pesticides kill all the birds, there will be no more birds to sing, thus spring will be "silent" with no birds.
She became passionate about the cause when she received a letter from a friend who had observed a number of birds who had been killed when DDT had been sprayed as a pesticide.
Carson accused industries of spreading misinformation and she also accused public officials of believing industry claims without any proof. She believed that uncontrolled use of pesticides was harming and even killing not only animals and birds, but also humans.
The book is famous for helping to launch the modern environmental movement. In fact, "Silent Spring" instigated the ban of DDT for agricultural use in the early 1970's, and JFK started a government initiative after reading this book which led to more pesticide regulations in the USA.