If you relax the the rules, I'll bring up David Attenborough. (I haven't read any other books than his Life on Earth, The Living Planet about the same subject (showing a zoomed-out view of the plant and animal life on the whole planet) but they absolutely dominated this type of market in the 1980's, I don't think there were even many alternatives published. Later on my interests turned away from zoology and botany.)
I'll second the recommendation to relax this rule. I think the ability to gauge the quality of a popular book is a lot more cross-domain than with textbooks. I've read good books and I've read bad books. I can tell pretty quickly if a book is bad, even if I'm relatively new to the subject area.
Also, I feel like a lot of people would tend to only read one or two pop books in a particular area. Any more knowledge beyond that often comes from the internet or a textbook or elsewhere. I mean, I can count on one hand the number of specific subjects about which ...
I enjoy reading popular-level books on a wide variety of subjects, and I love getting new book recommendations. In the spirit of lukeprog's The Best Textbooks on Every Subject, can we put together a list of the best popular books on every subject?
Here's what I mean by popular-level books: