I recently discovered the Open Syllabus Project, a site that crawls the web looking for syllabuses and then looks at what texts are being used in the class. From this, they prepared ordered lists. While the Project openly admits that their methodology is not perfect [*], it can be considered somewhat representative of what texts are being used and to what degree. Can it accurately split the difference between #11 and #12 on the list? Probably not. But they should be able to clearly differentiate between #1 and #100.
You can filter the list by different fields. When the "Chemistry" filter is applied, the #1 text is "Chemistry: The Central Science" by Brown, et al. No surprise there - it's the text I use and I've always heard that it is extremely popular. There are 3 other General Chemistry texts in the top 10, as well as 4 Organic texts, 1 P-Chem text and 1 Analytical text, which is also not too far from what I would expect. Enrollment in upper level chemistry classes is always much smaller since all the premeds and other nonmajors have left, so P-Chem, Analytical and Inorganic would be expected to be lower.
Being a polymer chemist, I'm curious where the first polymer chemistry text is on the list. It's a disappointing #122 - Polymers: Chemistry and Physics of Modern Materials by J. M. G. Cowie. In fact, there are 9 biochem texts higher on the list than this. 9! Apparently polymer chemistry classes are quite rare, about as rare as the polymerization of a non-terminal olefin. Augsburg College, where I teach, doesn't have a polymer chemistry class (despite my efforts to create and teach one), and I suspect that that is true elsewhere given the data above.
This is all just another example of how lonely it is to be a polymer chemist. If you want to be rich and/or famous for writing a chemistry textbook, write one for General, Organic, Physical, Inorganic or Bio-chemistry. ANYTHING but polymer chemistry.
[*] Of that I'm sure. The syllabus for the class I teach is only available on the college's internal website - no webcrawlers allowed.