Alternative world (or secondary world) fantasy gets all the attention these days as the quintessential owner of the steepest learning curves, but those expositionary slopes are molehills compared to the mountainous terrain to be conquered in the hardest of science fiction that the genre has to offer, like Garfinkle's All of an Instant.
Dragon’s Hoard Release and Author’s Note
It takes a certain arrogance to be an author, an arrogance to believe that you have stories worth telling, stories that other people should want to read and enjoy, and, perhaps more importantly, an arrogance to keep believing that through what is inevitably a lengthy process of submission and rejection before publication.
IGC Publishing 