My memory has faded of the details of the previously published stories, which you may not have read anyway, so I can't really detail the changes. The novel as it is now takes Oates through his culture shock at the gender and ethnic emancipation of the twenty-first century, through a passionate love affair and then a daring rescue of his lover from an alien planet. It is actually much better than that makes it sound, with Clough's memorable depiction of Oates as fish-out-of-water the best part of the book, though her alien intelligence is unusual and memorable also.
I did wonder whether Oates could have been as emotionally inexperienced as Clough depicted him. He died on or about his 32nd birthday, having fought in the Boer War, and it seems rather improbable that he had never encountered female intimacy beforehand. Recent research suggests a very different, much more sordid story though with admittedly little evidence. Of course, Clough's story is about her imagined Oates rather than a historical reconstruction; and my own family of that generation had plenty of British army officers of that age who married late or not at all - my own grandfather, born like Oates in 1880, and who fought also like Oates in the Boer War (though had the dubious pleasure of living on to fight again at Gallipoli) met and married my grandmother at the age of 47; only two of his eight brothers ever got hitched, as far as we know, though several others survived to adulthood.
It's a bit surprising that no paper publisher has picked up on Revise the World. Thanks to the internets it is available from Book View Cafe here. I'm also sorry that Clough didn't keep the excellent title of the original Hugo- and Nebula-shortlisted novella, "May Be Some Time", for the novel-length expansion. It is a book that deserved to be better known.