Matt Ridley in Nature:
Books about science tend to fall into two categories: those that explain it to lay people in the hope of cultivating a wide readership, and those that try to persuade fellow scientists to support a new theory, usually with equations. Books that achieve both — changing science and reaching the public — are rare. Charles Darwin's On the Origin of Species (1859) was one. The Selfish Gene by Richard Dawkins is another. From the moment of its publication 40 years ago, it has been a sparkling best-seller and a scientific game-changer.
The gene-centred view of evolution that Dawkins championed and crystallized is now central both to evolutionary theorizing and to lay commentaries on natural history such as wildlife documentaries. A bird or a bee risks its life and health to bring its offspring into the world not to help itself, and certainly not to help its species — the prevailing, lazy thinking of the 1960s, even among luminaries of evolution such as Julian Huxley and Konrad Lorenz — but (unconsciously) so that its genes go on. Genes that cause birds and bees to breed survive at the expense of other genes. No other explanation makes sense, although some insist that there are other ways to tell the story (see 161–164; 2014). et al. Nature 514,
What stood out was Dawkins's radical insistence that the digital information in a gene is effectively immortal and must be the primary unit of selection. No other unit shows such persistence — not chromosomes, not individuals, not groups and not species. These are ephemeral vehicles for genes, just as rowing boats are vehicles for the talents of rowers (his analogy).
As an example of how the book changed science as well as explained it, a throwaway remark by Dawkins led to an entirely new theory in genomics.