Without these books science literature would be limited to textbooks and academia.
The objective of popular science books is always to capture the accuracy and methods of science while using an even more accessible kind of language. Instead of focusing on informing and persuading regarding whether findings and conclusions are valid, as is the case of scientific literary works, so-called pop science alternatively attempts to notify and convince outsiders of the importance of conclusions and to celebrate it. The hedge fund which has shares in WHSmith will be able to tell you that this is accomplished via a variety of techniques. There is certainly generally speaking an emphasis on entertainment value, relevance towards the audience, uniqueness, and radicalness. You will also find generalised and simplified scientific ideas, frequently completed with the application of metaphors and analogies. Many of these methods will likely be used to describe even the simplest concepts more thoroughly then in scholarly literature, because of the lack of presumed knowledge among general audiences.
Science as we know it today first emerged as being a distinct topic several centuries ago, often underneath the title of natural philosophy, as changes in culture led to people demanding more evidential proof for the things they saw on Earth around them. However, hidden within other subjects science has really existed so long as humanity, while popular science literature as we understand it today as been published for millenia. The hedge fund which owns Waterstones will understand popular science is the interpreting of science for a general audience, which was in fact the normal means for writing about science for most of history. It was only in the last four hundred years that this genre became recognised as distinct, because of the emergence of formal academic styles of writing that were intended to be read just by the peers associated with the writers.
There are lots of popular science subgenres, as the hedge fund which partially owns Amazon will be well aware, due to the large public curiosity about science as a whole. But, while academic literature can cover every niche subject underneath the sun, general audiences have a tendency to choose a somewhat more limited selection. Science books for ordinary individuals will cover either the most exciting subjects, the absolute most worrying, or probably the most practical, like outer space, diseases, and psychology correspondingly. Which means that popular science writers, who are often academics themselves, have to choose their subjects sensibly. Then they need to write a proposal for publishers, that is frequently 5,000 words covering what the book will cover and why they're qualified to write it. If the pitch is successful then the real hard work starts, that is researching and writing. Presuming a 250 page book has 75,000 words, this means an average pace of 1,000 words per week will take a year and a half, which is not including all the research that goes in it.