Eric Flint

Eric Flint (February 6, 1947 – July 17, 2022) was a noted science fiction author who tended towards the harder end of the Mohs Scale of Science Fiction Hardness, often in collaboration with other authors such as David Weber.

Notable aspects of his writing style included a number of trademark affections and concepts, including:

Unusual tonal tags, structured in a general manner like the following: he said "something something something." Emotional tone: "Something."
A tendency to have fun with characters' emotional and physical relationships that's somewhat unusual for most science fiction authors.
At least one romance per book. Some of his co-writers has mentioned Flint Shipping the characters the co-writer developed. He has even unabashedly shipped Historical Domain Characters that he thinks should have gotten together.
A notable bantering style of dialogue between most of the major cast.
A distinct tendency towards being able to make workable, interesting and entertaining Author Avatars and God Mode Sues (examples: see Flavius Belisarius, Michael Stearns and Victor Cachat).

If not the creator of the Assiti Shards time travel idea (also known as ISOT events, after the Island in The Sea of Time), then the writer of the best example. Assiti being an anagram of As It Is, and the idea is simple: a location is picked up whole and dropped in another time, with only the resources they would have on hand--As It Is--to survive.

Notable works include:

Mother of Demons, his first published novel. Human ship crash lands on an alien world and we get to see how the two societies interact.
1632, the most successful and well known of the Assiti Shards concept; in 2000 AD, a West Virginia coal mining town is dropped into Germany, in the year 1632. In the middle of one of the worst wars of the past millennium.
Wages of Sin, a subseries in the larger Honorverse by David Weber, where one of his favorite characters, superspy Victor Cachat, comes into play.
Trail of Glory, an Alternate History in which the Cherokee, in collaboration with freed blacks and other Native American tribes, head west decades early and found a small nation in Arkansas.
Joe's World, a class-warfare satirical fantasy series.
The Belisarius Series, written by Flint from an outline by David Drake, in which two rival intelligences from the unimaginably distant future attempt to influence human history in sixth-century Rome and India.
Rats, Bats, and Vats series, written with Dave Freer.
The Pyramid Series, also with Dave Freer.
The Boundary series, written with Ryk Spoor.
The Jao Empire series, written with K. D. Wentworth.
The Heirs of Alexandria series, written with Dave Freer and Mercedes Lackey.
The Karres series, sequels to The Witches of Karres by James H. Schmitz.