A co-worker heard Harry Turtledove talking at Loscon about a “too hot to publish” alternate history in which Muhammad becomes a Christian. He wanted to read it and couldn’t remember the name. The story didn’t ring a bell with me, but I knew Harry would be glad to answer the question.

There would be a minor catch in admitting to one of my favorite writers that I haven’t actually read everything he’s written, but that was just my pride getting in the way. It seems I’m still holding onto the self-image of being the kind of hyperfan who combed used bookstores hunting down every Poul Anderson story ever published. Am I worthy of calling someone a “favorite writer” if I’m not doing that sort of thing? However, I reminded myself, in those days I didn’t work for a living. Funny how a job takes up your time.   

Harry was able to put his finger on the story immediately:

I think the story your coworker is talking about is “Departures,” which ran in the January ’89 Asimov’s and is reprinted in my collection called — after it — Departures. It’s about Muhammad the monk leaving Syria as the Persian invasion rolls in. The coworker might also be interested in Agent of Byzantium, which has stories set in a universe based on what happened after that change.

His answer made me curious to know more. Google located Steven H. Silver’s interesting review of Departures on SF Site:

The title story [Departures] is one of the more traditional alternate histories to appear in the book and, although it is not included in Agent of Byzantium, it does set up that entire story sequence, making Mohammed a monk gifted with the ability to write beautiful hymns. Although the story only begins to look at the results of such a world, the effects can be seen in “Pillar of Cloud, Pillar of Fire,” the last of the Basil Argyros stories in which Turtledove’s spy visits the Great Library of Alexandria. If you haven’t read Agent of Byzantium, this story gives a good example of the stories which appear in that book.

I’ll be looking online for a copy in a day or two. (Wonder if it’s available on the Kindle?)