I’ve recently finished reading the first three books of the Barsoom series by Edgar Rice Burroughs. The Barsoom books are early 20th century pulp science fiction stories. The first three books center around John Carter, a man from Virginia who one day miraculously awakes on Mars.
The books are full of fast-paced action. Especially the second book, “Gods of Mars”, which covers but a few days, gives John Carter and the reader barely a moment to relax, with one more complication after each battle won, and the hero always one step behind the villains.
While the constant bloodshed shows that it’s not a tale of the 21st century, it is probably one of the first modern science fiction stories. It is also modern in some of its messages – the hero fights superstition and belief in false gods, and unifies the different races of Mars.