Four common Bookshelf Detective critiques that go against the spirit of this community.
1. "So... how many of these have you actually read?"
Anyone who genuinely loves books buys way more books than they can read in one lifetime. The unread shelf isn't a failure of discipline. Stop asking this, it's the "do you even lift bro" of literacy.
2. "You know female authors exist, right?"
Representation in publishing is a real issue worth fighting for. Sniping at a stranger's shelf does nothing to help that cause except make them defensive. Maybe try to open the poster to new experiences if you feel like making this comment: "I see you like X, you'd probably love Y." A recommendation converts; a "gotcha" closes.
3. Owning Ayn Rand (etc) on its own is not a red flag.
I promise you: I hate Objectivism more than you do. But we have to remember that owning a single book does not reflect a worldview, and Rand's classic "coworker" book is thrust on so many. Look at the bigger collection, not the one-off.
4. Going deep on one lane is totally normal. .
Horror, romance, manga, dick lit, weird girl fiction: curating a sub-genre is just so normal. Not everyone owns a room big enough to perform the full range of human letters, and honestly, the guy with 400 spine-matched paperbacks in one genre is probably more serious reader than the guy with one of everything.
Take all these together, and it all comes down to Taste. I always think of the Bourdieu quote: “Taste is first and foremost distaste, disgust and visceral intolerance of the taste of others.” Which essentially means that all four of these critiques are a class/status move dressed up as insight. It says more about you than it ever will about the poster.