On Fridays the traffic to the Triborough Bridge backs all the way down to my Upper West Side neighborhood. All those S.U.V.’s and the occasional, top-down convertible, spinning their wheels on Broadway or Amsterdam Avenue in the late afternoon heat — fleeing the city as if they were running from a plague.

I don’t mind being left behind. I usually leave the city at some point in August, but I’ve never taken a share at some house in the Hamptons or anywhere else that required my presence every weekend. I’m one of those odd individuals who actually likes summer in New York, especially once the great caravan has moved on and emptied Manhattan. It allows me to enjoy that rarest of urban pleasures, to be alone in the city.

This sudden solitude has been known to fill one with a certain, giddy feeling of freedom, with the sense that all the world has been left at one’s doorstep. It is responsible for many celebrated flights of fancy, from Tom Ewell lusting after Marilyn Monroe in “The Seven Year Itch,” to F. Scott Fitzgerald’s Nick Carraway picking out “romantic women” and imagining following them “to their apartments on the corners of hidden streets, [where] they turned and smiled back at me before they faded through a door into warm darkness.” Judge Joseph F. Crater, interrupting a Maine vacation to return to the sweltering city in August 1930, got completely carried away, and mysteriously disappeared forever.

Those of us with a less active imagination or a happier marriage embrace the more quotidian pleasures that the city allows. I relish how the whole pace of my neighborhood slows markedly, how the traffic lessens after those frenzied, Friday afternoons. Stepping outside on a summer weekend morning, New York can seem startlingly, even shockingly quiet. Everything seems to run slower, even electronic and mechanical devices — my sluggish computer, the already balky elevator in my building.

I move more slowly, too, taking the time to stop and look over things I normally pass by. There is a hidden stairway trailing down into the shadows below street level. The sanctuary of a church opened to the street, the high, stained-glass windows gleaming in the darkened sanctuary; the close, musty church smell of carpet, candles and books wafting out onto the sidewalk. Plaster heads, used to decorate a building a century or so ago, leer out from where they’ve always been, just a little ways above my line of vision.

One of my favorite sidewalk activities is to stop and browse the makeshift book stands that proliferate in my neighborhood. This is a dangerous pastime for a New Yorker such as myself, whose home is already beginning to bear an unnerving resemblance to that of the Collyer brothers. I use the booksellers as a circulating library, giving away as many volumes as I can stand to part with, but always picking up another one or two in the end; such great bargains for a dollar!

But whether I buy or not, I like to look at the books they are selling. So often in New York, one can find what is obviously someone’s entire library out on the street — no doubt gleaned from one of those apartments described as “estate condition” in the listings.

These collections are like brief trips back in time, little windows into other lives. Remember when that school of psychology was in fashion, that burning political issue? That typeface, that style of cover? Here are somber, plain book jackets from the 50’s; garish, psychedelic colors and script from the 70’s. Whole shelves of books on a single subject: the future of the Soviet Union, the role of women in education, black nationalism, sexual theory and technique, method acting, gestalt therapy and the secret of wok cooking.

Here are all the preoccupations and intellectual fads of the last 50 years, at least. We can smile with the condescension of the present as we pass by, knowing how it all turned out, how this or that trend passed without altering very much at all. Yet it seems almost obscene to see someone’s life exposed this way, put out on a sidewalk table or blanket for all who pass by to see and handle. These books belonged, after all, to our neighbors, maybe people we saw on the street every day for years until, without really noticing, we did not. They, too, have gone on, one way or another, leaving us to enjoy the emptier city.