So much of what we encounter each day is designed to influence our decisions and purchases, but the books on this shelf have no agenda. They are not being pushed by the publishing industry. There is no marketing budget behind them. They’re not trending on my social-media feeds or selected by a recommendation algorithm. They were not chosen to signal anyone’s intellect or righteousness or in-the-know-ness. They are often old and very often ugly. I’ve come to think of this shelf as an escape from hype, a kind of anti-curation.

When I pick the books up, a part of me expects them to be warm, like a just-vacated seat. They often still contain the life detritus of the last person to open them: makeshift bookmarks, boarding passes or receipts; oil stains or flecks of melted chocolate or even blood; an eyelash. Sometimes the books make me itchy, and I know the last borrower owns a dog. Sometimes there are clusters of related books that must have been checked out by the same patron. It’s like getting to look at someone’s night stand, but whose? The shelf is everyone’s night stand, an average of night stands. Once I spotted a distinct group of lyric-essay collections, all of which I owned or had read, and thought they must have been returned by someone I knew.

On a recent trip to the library, I took photos of all the books on this shelf with my phone, to study in detail at home. Between a book about treehouses and one called “Star Wars Made Easy” (is “Star Wars” hard?), I saw one called simply “Plague.” (How had I not noticed it while taking the picture? For months I’d been researching epidemics for a piece I called “the plague essay” in my mind.) Above that was a book I remembered seeing on my own coffee table not long ago, pink jellyfish on a blue background. Had my own husband, a lover of aquatic life, just returned it? (We’d recently picked up “Other Minds,” a book about how octopuses think, from this same shelf.) Or were multiple readers in Denver suddenly drawn to oceanic invertebrates at the same time?

I have taken books from this shelf I never would have sought out otherwise. One was by Rachael Ray, grabbed on impulse in a rush to get home and make dinner. It turned out not to be just a cookbook, but a kind of food diary, recording her meals for a year, full of nonprofessional snapshots: the dishes she cooks for her husband over and over, multiple variations on deviled eggs, her mother’s requests on holidays. It demonstrated a sort of recursive model for cooking, where bits of yesterday’s dinner end up in tonight’s, and bits of tonight’s in tomorrow’s and so on — as if you’re giving your food a sense of memory. Years later, I still think about it; I found it surprisingly poignant.

It wasn’t the first time a recently returned book had infiltrated my thinking. On an earlier occasion, I found on this shelf an orange paperback called “What Should We Be Worried About?” in which dozens of scientists and scholars pontificate about which threats to human existence are the most urgent. What anxious individual was out there in the city, questioning, like me, if her anxieties were misplaced, if she was worrying right? I never read the book, but I kept it around for weeks, looking at the spine and meditating on the title: What should we be worried about? Then it was due, and back on the returns shelf it went.