Brown bagging books

I'm curious about opinions on brown bagging books with questionable covers/adult content.

I have a selection of historical books on my shelf and there are a few with imagery on the spine that im not sure i want my newborn son being exposed to without context.

While I understand the historical significance of such books and have never had any prior inclination to hide them.(i read them after all.) I find myself now considering concealing the spines.

Can I have some lf your opinions? Thoughts? Criteria? Distain?