My 1st reason is he's got a better handle on the idea of melding fact with fiction than any contemporary author I've heretofore encountered. That's for true. But whenever you're talking about fiction and history you're entering a potentially scary realm, so says I. Because what's the point of bringing history into a story if you're not going to go to some pains to represent it adequately accurately? Tell it sans history, or go the other way and write alternative history fiction such as Steampunk, or whatever, I don't care. That's beside the point in the case of Jim Shepard because he goes for as much stick-to- the-record as is possible.
He also 2ndly tells wildly imaginative stories, very well evidenced by the collection "Like You'd Understand, Anyway." And the best news of all is he has a new collection being published by Knopf and coming out next January. It's called, "You Think That's Bad" -- which I doubt I will think that's bad.
As someone who writes & someone who likes history in fiction & thus struggles to find the best way to balance the two, I turned to Jim Shepard, who is as I've said kind of THE authority on this subject. I emailed him this specific question, "How do you comfortably blur the line between fact and fiction? That is, when do you give up verisimilitude and go ahead and tell the story, history be damned?" He replied as follows:
I try to stay as close to the historical record as I can. And I also choose situations that usually leave me room to maneuver: what went on inside the superstructure of the Hindenburg right before it blew? Nobody knows. Usually the way I operate, I've noticed, is to stick pretty faithfully to the historical narrative as I come to believe it, after all of my investigations (and it also helps to remember that historians themselves often disagree) but to invent freely when it comes to inner lives. So that, going back to Love and Hydrogen, I want to be absolutely accurate about what my two crew members' responsibilities onboard were, but I'm inventing their love affair.
To which I say, ok, I'll buy it.