Do you find yourself reacting - positively or negatively - to what other people read?
I'm interested in the idea of how we judge other people around books. Not so much about whether books are highbrow or trashy. More about if you feel an author's political/social views or their reputation means you couldn't enjoy their books - and you'd also feel distanced from anyone who had bought their books and enjoyed them.
Alternatively you might think, 'Oh if they've bought X's new novel or non-fiction book they must be alright and I want to get to know them better...'