Yeah, as a rule of thumb for rationality, if you only have two buckets, you haven't thought about the topic critically enough.
For books, there's a fairly simple explanation for a mental divide: elitism. Maybe you correlate ability to memorize trivia (which tends to be plentiful in books trying to illustrate some overarching point) with "culturedness". Or maybe the correlation comes from name dropping prolific authors (common in humanities, because certain authors "represent" certain schools of thought). Etc.
In my personal experience, the book reading anecdote doesn't really hold because a lot of people I know simply have complex backgrounds (e.g. living large portions of their lives in two or more different countries) and that alone can bring a lot of color to discussions.
As a rule of thumb for rationality, buckets are mental models -- tools -- and can be treated as such. Drawing a dichotomy, while incomplete, can be useful given the balance between accuracy and parsimony.
For books, there's a fairly simple explanation for a mental divide: elitism. Maybe you correlate ability to memorize trivia (which tends to be plentiful in books trying to illustrate some overarching point) with "culturedness". Or maybe the correlation comes from name dropping prolific authors (common in humanities, because certain authors "represent" certain schools of thought). Etc.
In my personal experience, the book reading anecdote doesn't really hold because a lot of people I know simply have complex backgrounds (e.g. living large portions of their lives in two or more different countries) and that alone can bring a lot of color to discussions.