'Down in the Bottomlands' is a novella written by Harry Turtledove which takes places in an alternative history in which the Atlantic Ocean did not reflood the Mediterranean Sea 5.5 million years ago in the Miocene Epoch, as it did in our history. The Mediterranean Basin thus remains dry to the present day in this time line, as a vast sunken desert called the Bottomlands, averaging nearly two kilometers below mean sea level, with summer temperatures reaching well above 40 °C and with little or no rainfall.
Martin Padway, 20th-century archaeologist, becomes a reluctant one-way time-traveller, landing in Rome on the verge of the Dark Ages. With no way home, he sets out to make the world he's in a better place. In short order, Padway "invents" and introduces such things as Printing and newspapers, Arabic numerals, Double entry bookkeeping, Copernican astronomy, and, most important -- Distilling. And the world of decaying Rome will never be the same!
BOOK ONE — THE ROARING TRUMPET BOOK TWO — THE MATHEMATICS OF MAGIC