Terry Brooks' Shannara as a whole, with the Druid order being the only people with any knowledge of technology left. Specifically, the most recent Genesis of Shannara trilogy, which aside from the usual scavenging for supplies includes sports stadiums as the last organized holdouts of civilization.
Ciaphas Cain: An apt example of the level of superstition around machinery can be found in the novels. At one point a techpriest worries about whether a device will work when she doesn't have any incense to light first, of course it does. Said techpriest is also something of a black sheep when we meet her because her rather pragmatic and creative approach is seen as a failure to understand the theology. Which of course had limited her advancement.
Cain himself wonders, after building an IED in Death or Glory, if it can really work without a techpriest's blessing. He decides that killing Orks is "the Emperor's work", and He will probably cut Cain some slack on this.
The parts of Stephen King's The Dark Tower set in Mid-World have this flavor. It tends to become both more prominent and more dangerous as the series goes on: in the first couple of books Roland's six-guns are rare and precious artifacts, but by the fifth we've seen working robots, giant cyborg bears, weaponized Harry Potter props, and a supersonic maglev train with a yen for riddles, all of which are decaying and homicidal.
Earth Abides by George Rippey Stewart deals with the consequence of most of the human population being wiped out by some plague. The protagonist sees mankind's technological advances undone, because the scattered survivors do not have the cohesion, nor the education or even the motivation to keep the technological marvels (electricity, indoor plumbing, metalworking etc.) running. Humanity reverts to a hunter-gatherer society.
Curiously, we do meet a family of semi-literate farm-laborers somewhere in the Southern US who look like they're just going to carry on working the land as they have for generations (indeed, their situation may have improved insofar as they aren't working for someone else any more). They're only mentioned again at the end of the book...generations after their encounter with the protagonist, their descendants still grow cotton for their departed masters despite not having the knowledge or technology to use cotton for themselves. There's also a Native American settlement in New Mexico and a cult in southern California that both appear pretty well-organized and self-sufficient.
In The Sundered by Ruthanne Reid, there is a whole industry made out of scavenging things to sell. When the main characters find a cache of guns, they are overjoyed because nobody had even seen any in years.
The People of Sparks takes place somewhere in the United States about 250 years after several successive wars and pandemics, where descendants of the survivors have reverted to old-style farming settlements, sending out 'roamers' to search pre-Disaster houses and such for supplies such as clothes.
In The Lord of the Rings, the kingdom of Gondor has ancient cities and monuments constructed by means lost to the current dwellers due to technological regression.
In Life as We Knew It, by Susan Beth Pfeffer, the United States is on its way to becoming like this after an asteroid hits the moon and causes climate change around the world.
Cormac McCarthy's The Road is exactly this. The story follows a man and his son walking south through the ash-covered ruins of America after an unspecified cataclysm, scavenging whatever food they can find and avoiding bandits who steal and murder to survive. Many people have even resorted to cannibalism.
Also averted, since the novel goes on long enough that the world regains its mastery of science. It's heavily implied that the remnants of technology the monks preserved was instrumental in the reconstruction of a technologically advanced society. (Whether or not this is a good thing is left as an open question).
The Kinetic Novel Planetarian also takes place After the End and involves Junkers, with one critical difference: instead of restoring technology, the Junkers pilfer it (as well as other valuables) from the ruins for fun and profit. Well, as fun as dodging autonomous killer robots can be, anyway.
Somewhat averted by S.M. Stirling's Emberverse series. The laws of physics have been altered by the Universal Mind having an argument with itself so that electrical circuits, internal combustion engines, gunpowder, and nuclear decay no longer function as expected, leading to the collapse of civilization. But still the wreckage of technological society is useful: the survivors scavenge the wreckage for useable parts and metal alloys difficult or impossible to manufacture under the new conditions. The results are swords made from automobile leaf springs, catapults powered by heavy duty springs salvaged from truck chassis, windmills and water wheels using gears salvaged from automotive transmissions, etc.
So far the Emberverse is only 28 years into the Change, so a lot of the more durable stuff like the machine parts mentioned above are still in play, and more valuable soft goods like books are being preserved in most civilized areas (a few universities are mentioned to have survived, so at least the knowledge of high-tech society has been preserved). How well things are preserved down the line is still very much up in the air.
Alice, Girl from the Future features a planet which suffered a collective memory loss 300 years ago. The king uses a dentist's chair as a throne... his guards are using chamberpots as helmets.
Theodore Cogswell's story The Spectre General extends the concept to an interstellar scale, with a Galactic Protectorate rising on the ruins of The Empire and using technology it can no longer duplicate or reliably maintain until it makes contact with a lost outpost that has preserved the old technical knowledge.
Death Lands. The Trader specialises in tracking down Stockpiles left by the now defunct US government and selling the contents to the various Big Bad wannabies. As this included pre-Apocalpse weapons that can be used against him he now realises it was a major mistake.
In Ship Breaker by Paolo Bacigalupi, the world is like this. After Global Warming led to changes in sea levels, many cities were destroyed. The protagonist, Nailer, lives in what once was Louisiana and takes apart former oil rigs for scrap metal. They run into a problem when they find a ship that has a living person in it.
Also the short story The Calorie Man. Oil supplies have run out so the protagonist makes a living scavenging useful items from the now abandoned suburbs before they're reclaimed for cropland.
The multi-author Death Zone series (taking place in the same universe as S.T.A.L.K.E.R. but 50 years later) involves five anomalous zones which are formed after an unknown cataclysm wipes out 4 major cities (plus the Chernobyl Exclusion Zone) and covers the areas with gravity bubbles. The zones feature many anomalies and rogue nanotechnology, as well as survivors called stalkers scrounging for supplies and hunting for tech. Unlike a typical example of this trope, the outside world is mostly fine, and supplies are often smuggled into the zones. However, most of the novels barely feature anything beyond the zones, so the atmosphere of the stories often makes it seem as if there is nothing else.
In Robert Jordan's The Wheel of Time, many ancient arts have been lost, including the art of creating magical items (ter'angreal). In an unusual move, we actually see characters rediscovering many of the lost arts over the course of the series.
Zilpha Keatley Snyder implies this in the Green-Sky Trilogy. She describes several times how their great public buildings, palaces and temples, which involve some pretty complex engineering, were all built by teams joining their telekinetic powers together to lift heavy stuff. That "uniforce" ability has been lost for many generations. Now the Fridge Brilliance kicks in. These buildings are all made out of wood and vine in what is pretty much a rainforest planet. Stuff deteriorates very fast in these environments. Who's going to do the maintenance? Fortunately, The Magic Comes Back (or starts to) and by the end of the third book we're pretty sure they're going to be okay.
The Girl Who Owned A City combines this with Teenage Wasteland after a plague wipes out all the adults.
In Hatch - set in the Great Ship universe - several million refugees are trapped on the exterior hull of the Great Ship. Surrounding their city (built inside a sealed up rocket nozzle larger than the Earth) is the remains of the Polypond, which periodically spews out billions of biological and mechanical creatures. The refugees use needle-like ships (raiders) to harvest the creatures for building material, organics, and bits of technology.
Staying Behind, a short story by Ken Lui. Brain Uploading has caused the collapse of civilisation because most people chose to live forever in digital form. The protagonist tries to hold onto the living world, only for his children to desert to the Singularity. When he tries to stop them, his wife points out that he's nothing to offer them but a hard life picking over the technology of the old world until it runs out.
Zenna Henderson has a variant of this in Deluge, one of her novellas of The People and the only one to take place back on the Home world. With their Psychic Powers taking the place of labor-saving devices, they've simplified their daily lives to the point of minimalism. So when they find out the planet is about to explode and they need to get the heck out of there, they don't have the technology to do it. Fortunately, what they do have is scavenger minds — access to the memories of dead ancestors, going back thousands of years, to the days when they did have interstellar spacecraft. By taking time to Remember back that far, each person can learn the skills of an ancestor who, say, built the navigation instruments, or installed the toilets.
In the crapsack future England ("Inland") of Riddley Walker, the only source of iron is whatever rusting hulks of 20th-century machinery they can manage to dig out of the ground.
Dinner at Deviant's Palace is set after some cataclysm blew large radioactive holes in southern California and led to a collapse of society and Lost Common Knowledge. The current society is built largely around digging useful (or just neat-looking) stuff out of the rubble of the past. Some people drive cars as status symbols, but they're drawn by horses because there's no gasoline any more.
The world of Cthulhu Armageddon is one, explicitly compared to Mad Max and Fallout in the opening. The human race scrapes out a bare-bones existence living in those few structures not destroyed by the Great Old Ones' rising. Its notably also turned into a New Old WestWeird West.