Blood of Earth by Beth Cato, set in an alternate Steampunk 1900's San Francisco.
Laie Tidhar's Bookman series which combines real historical characters like Harry Houdini, original ones and fictional like Lucy Westenra and Mycroft Holmes. Oh and David Icke would be right in this universe, the British royal family really are alien reptiles, only it's not a conspiracy, everyone knows about it and most people are quite content. The French royals were too but they got overthrown by an alliance of humans and automatons.
Burton & Swinburne Series is set in an alternative history version of the world which ended up becoming much more advanced due to a time traveler going back in time and accidentally gets queen Victoria killed as well as accidentally telling someone about various technology from the future which ends up creating an alternative reality in which hybrid animals, highly advanced robots, and psychic powers exist.
Isaac Asimov's "C-Chute" is an early example, taking place on a steam-powered space ship.
Dawn of Steam shows us a world that is beginning to evolve from one like our own just after the Napoleonic War into a fully fledged steam punk setting. That being said the series still prominently depicts a Cool Airship and steam-fueled Power Armor.
The Neo-Victorian clade from The Diamond Age deliberately modelled their technology to be aesthetically Victorian and steampunk-ish despite having a full mastery of nanotechnology.
William Gibson and Bruce Sterling's 1990 Alternate History novel The Difference Engine, while not actually the first instance of Steam Punk, is credited with popularizing the genre in the west. It's also a lot more "punky" than the ones that followed, with its steam-driven Dickensia practically qualifying as a Dystopia. It was intentionally written as a Cyberpunk novel, set in a Victorian setting.
In the Doctor Who novel Imperial Moon — part of the Past Doctor Adventures series, steampunk technology is technically a key part of the plot, as the Fifth Doctor and Turlough learn of the existence of the British Imperial Spacefleet in 1878. While Turlough doubts the concept, the Doctor notes that technically Victorian Britain could have built a structurally sound spaceship but would have just been unable to get it airborne, with the engines depicted in the novel devised through indirect alien interference.
The Edge Chronicles occasionally dip into this aesthetic. And if they weren't steampunk before, they certainly are as of The Immortals. (Which makes sense, given that in that book the Edge is going through its equivalent of the Industrial Revolution.)
The Exile's Violin, by R. S. Hunter, the beginning of a planned "Tethys Chronicles" series.
S.S. Taylor's The Expeditioners takes place in an alternate present where computers were invented in the Gilded Age and crashed on a massive scale sometime in the early '80s leaving society to go back to older technologies.
The Falling Machine by Andrew P. Mayer (Book 1 of an ongoing trilogy) is about a Steampunk Superhero team called The Society of Paragons.
Theodore Judson's Fitzpatrick's War, a Roman à Clef of the life of Alexander the Great, takes place in a steampunk future environment. It's later revealed that this is because a secret society set up a Star Wars Defense Grid in space to fry any electronic devices on the planet's surface with giant lasers.
Older Than Radio: Anthony Trollope wrote mainly fairly realistic novels. But towards the end of his life, in the early 1880s, he wrote The Fixed Period which imagined a world of his future in which people got around on "steam-powered tricycles" and played cricket with "a mechanical steam bowler."
Dime Novel hero Frank Reade, like Wells and Verne, can be counted as another example of steam punk avant la lettre; the Reade stories are full of steam powered inventions of all kinds. Perhaps the most famous was The Steam Man of the Plains, a kind of proto-robot that could shoot fiery missiles. For that matter, Frank Reade can also be counted as actual steampunk, courtesy of Paul Guinan and Anina Bennett's FRANK READE: Adventures in the Age of Invention, a fictionalized biography of the Victorian inventor.
The His Dark Materials series includes steampunk elements, especially for Lyra's world. The trope is minimally deployed—and Pullman never goes out of his way to describe any obviously Steampunk technology or settings. For example, the power source of choice is electricity (referred to as anbaric power—from amber, which the Greeks call electrum) supplied by nuclear generators (atomcraft works—from the German Atomkraftwerk), and science is mostly working on particle physics. The book feels more steampunk than it is probably because the opening chapters take place in the rather old-fashioned University of Oxford, features a few incidental airships, and prominently features a cast of powerful politicians, aristocrats, industrialists, and explorers with high-flown titles who bestrode the world with a swagger and a Mighty Whitey self-confidence that can only be described as Victorian. Not to mention the almost Dickensian take on English class relations.
The film, on the other hand, plays the steampunk for all the trope's worth.
The TV series, however, averts this, featuring an overall more modern-looking aesthetic to Lyra's world.
K. W. Jeter's Infernal Devices (not to be confused with the Cassandra Clare novel), arguably the book that started it all. Contains mad scientists, space travel, time travel, clockwork robots, and fish-men!
Cassandra Clare's The Infernal Devices series is a Gaslamp Fantasy mixed with Steampunk elements. Set a century before her The Mortal Instruments universe, the books follow a young woman named Tessa as she attempts to deal with numerous magical plots against her as well as her friends. Technology is supplemented by magic in the books, making the trope of Steampunk Justified.
Stephen Hunt has his Jackelian Series, set in an Alternate History — very alternate — with airships, submersables, pneumatic buildings, steam-powered intelligent robots, flintlock pistols, gas masks, goggles, bionic characters...and mutants, fey creatures, aliens and practically everything else you could imagine. It starts with The Court of the Air, with follow-ups including The Kingdom Beyond the Waves, Rise of the Iron Moon, Secrets of the Fire Sea, Jack Cloudie and finally From the Deep of the Dark. Each novel is standalone with a few continuing characters.
The Land of Oz books, surprisingly enough. Yes, the place is loaded with magic, but it also has some interesting technological features like prosthetics (Nick Chopper, Captain Fyter), cell phones (The Wizard, on one of his return trips, whips one up), Ridiculously Human Robots (Tik-Tok), artificial life forms (ChopFyt), and cities that can sink or rise mechanically (plot point in Glinda of Oz).
Balogun Ojetade's Moses: The Chronicles of Harriet Tubman, an early work of what the author dubbed "steam funk" (black steam punk), has real life abolitionist Harriet Tubman fighting the forces of evil with superpowers in a steam punk alternative version of the US shortly after the assassination of Abraham Lincoln.
The Parasol Protectorate Series by Gail Carriger features heavy Steampunk elements, along with an alternate history London where supernaturals influence society.
The Pax BritanniaShared Universe, including Jonathan Green's series about Ulysses Quicksilver, Agent of the Empire, and Al Ewing's Mexican adventurer El Sombra (overlaps with Cattle Punk). Contains lots of Shout Outs.
In Ian McDonald's PlanesrunnerEarth 3 or E3 is a mix of this and Raygun gothid. Coal is the main fuel because there's no oil but there are no steam engines because the electric motor was invented first. There are airships but their gasbags are woven of carbon nanotubes, vehicles all operate off a power grid but their computers or "comptaters" use vacuum tubes. The protagonist refers to it as "electropunk".
In Please Don't Tell My Parents I'm a Supervillain, Penny's first invention, the Machine, is actually a wind-up device that consumes energy from any and all nearby sources rather than something more electronic. It's even mentioned to be filled with incredibly fine gears. Most of the rest of the things she makes aren't steam punk, though.
Queen Victoria's Bomb by Ronald W. Clark, about the invention of an atomic bomb a hundred years earlier. It has limited consequence however, as knowledge of the invention is suppressed by the Queen.
Several of Robert Rankin's novels are set in/relate to a high-tech Victorian age whose history was supressed by those fiendish witches The Chiswick Townswomen's Guild.
L. E. Modessitt's Recluce saga flirts with the genre. It never quite gets there, however; the leadership of the titular nation deliberately withholds the steam-based technology from general knowledge in an effort to preserve the status quo. But that doesn't stop things from getting out of hand in The Death of Chaos entry in the series.
Spanish book La República Pneumática takes place in a Roman Republic restablished by Emperor Claudius, thanks to the steam (or pneuma) technology developed by Hero of Alexandria. The steam certainly changed things — trains and zeppelins are common, and coal-powered automatons are toys — but did nothing for many other issues — corruption is high as hell, and slavery is still rampant. The story takes place in the days leading to the 1000th anniversary of Rome's foundation, the protagonist being a young teenager that gets accidentally involved in a conspiracy to murder the Consul.
One of the parallel worlds in Sergey Lukyanenko's Rough Draft duology is an example of this trope. Earth 3 (AKA Veroz) lacks petroleum, thus preventing the jump to internal combustion and the development of any petroleum-based products (including plastics). At one point, the protagonist witnesses a steam tank defending a coastal city-state (nation-states do not exist in this world) from a kraken.
A slight example in Lukyanenko's Borderlands, where the once-powerful world of Centrum has been reduced to this after a petroleum-consuming plague has been unleashed on the world, destroying all oil-based products (including plastics) in a matter of hours. Electricity is practically non-existent, as plastics allow for cheap insulation of wires. Without them, other types of insulation are simply not cost-effective. Old steam trains are brought back into service, and the railroaders become the most powerful NGO in Centrum, as all supplies and trade are dependent on them. Modern-day guns still work, though (at least, those that don't have any plastic parts).
Andrew Mayers Society of Steam series which is about steam powered superheroes and villains in the Gilded Age.
Steampunk meets Robot Uprising in the short story Trois morceaux en forme de mechanika by Gord Sellar, in which an uprising of mechanikae beginning in 1897 Bohemia leads to the destruction of humanity and their culture, with a melancholy aftermath as the robots try to come to terms with what they've done through art and music.
William Pene Du Bois'  has a lot of steampunk sensibilities in its descriptions of wonderful, but useless late-1800s steam-powered gadgetry, including a bed with infinite sheets and an electrified room where the furniture can be driven via bumper-car technology. There's also a dash of Cool Airship in its many balloon devices.
Jules Verne's 20,000 Leagues Under the Sea, set in Victorian times and featuring a technologically advanced submarine, would qualify if not for the minor detail that the book was written during the Victorian era.
S. M. Peters's Whitechapel Gods has a Steampunk god, in addition to a clockwork counterpart, both of them with their own armies of coal-driven and clockwork soldiers, respectively. This particular novel draws heavily on the "punk" park of Steampunk; it's not a happy place.
The Wraith Knight series by C.T. Phipps is an unusual example as it takes place in a High Fantasy setting but which has combined technology with magic after the last war between the Dark Lord and The Alliance. While the protagonist is effectively a Ringwraith, he has to deal with an enormous clockwork spider and the flying navy of the Empress.