Harry Turtledove is the dean of alternate history or "counter-factual" novels, which hinge on something happening differently than it did in real life, S.M. Stirling has some entertaining work of his own in the field. The Peshawar Lancers is a fine example. After a massive meteor strike in the 1870's devastated most of the Northern Hemisphere, the British Empire survived by relocating most of its royalty and leadership to its holdings in India. The catastrophe meant that technology developed much more slowly than it did in our world, and things such as automobiles and computers (immense, steam-powered "difference engines," as envisioned by Charles Babbage) are rare even in 2025, when our story is set. Captain Athelstane King, a dashing soldier and adventurer that would do any Victorian novel proud, is ensnared in a plot against his nation and himself, with the unscrupulous Russian Czar and his minions at its heart. Swordplay, fights on horseback and a duel atop a dirigible offer rollicking fun and Stirling never lets the story sit around or rev in neutral.
-----David Baldacci has written several crime/espionage thrillers, and started a series on 2003 that features Sean King and Michelle Maxwell, a pair of whip-smart, uber-competent private contractors -- and former Secret Service agents -- who solve crimes, rescue folks and generally get paid for poking their noses into things. In Simple Genius, King sets out to investigate a murder at a private think-tank exploring a whole new kind of computing that may lead to artificial intelligence. The think-tank is located across a river from a secret CIA training base and the geniuses aren't talking. The dead man's daughter is, but she doesn't communicate well to start with and her father's death has further unsettled her, so no one knows what she's saying. Maxwell tries to deal with personal issues that have brought her to her breaking point. Baldacci writes a serviceable thriller, but he strays out of his depth when he tries to make Maxwell's issues believable. But the action moves quickly, features a couple of unforeseen twists and gets from page one to "the end" in fine style.
-----Douglas Preston's Blasphemy is an excellent example of a book that one might wish handy when one needs kindling, but there's a good chance the fire would say, "No thanks. I have standards." Preston usually writes with a partner, Lincoln Child, and I've never read any of those novels. After Blasphemy, I'm never going to. Wyman Ford, former CIA agent who lost his wife in a car bombing and spent several years in a monastery afterwards, works as a private investigator. He's hired by White House officials to look into an immense particle collider project in Arizona, code-named Isabella. Despite the presence of the brilliant Gregory Hazelius, the project isn't going as planned, and the President is worried its failure could hurt him in the election (you may remember how ending the Superconducting Super Collider project nearly kept Bill Clinton from winning a second term - not) Ford discovers that the scientists, including a former ladylove, are indeed hiding something. The project becomes a political football when an unscrupulous lobbyist and greedy televangelist decide to use it for their own ends. And there are some Navajo Indians involved as well, protesting the Isabella project itself.
Preston introduces no fewer than 12 scientists on the project, not one of whom has any more depth than the pages they're printed on. His main characters fare no better. Some folks griped that the novel featured a greedy televangelist and a religious nut as its villains. But frankly, anyone who's a member of any group or profession found in this novel could be just as justifiably insulted by how they're depicted if they could force themselves to tramp through Blasphemy's poorly-written, lightly edited pages. A character subsides into unconsciousness at one point, and we read that "darkness descended gratefully." I, like you but unlike either Preston or his editor, was unaware darkness could express gratitude: I thought it was just the absence of light. Blasphemy boasts a preposterous, see-it-coming-from-miles away ending that puts a proper capstone on a true drudgery of a reading experience.