Update: WBIE now says that the issue with Steam Family Sharing has now been resolved for all players, "including those who were impacted previously." We re-tested it ourselves, and can confirm that sharing is now working properly.
Steam Family Sharing was announced in 2013 as a way for friends and family to share their game libraries with one another. There are some limitations, but basically you can give access to your entire Steam library to up to five people across ten devices. Not all games support the feature, however, and according to Reddit, Middle-earth: Shadow of War is one of them.
"My friend and I alternatively buy all the good games and share amongst ourselves, but this game doesn't support sharing," DoorHandleWalah wrote. "We had to refund the game because of that."
"Had to" is maybe overstating it a bit, but there is nonetheless a good deal of anger over the news in the comments, perhaps because it comes on top of controversy over Shadow of War's loot boxes (which as it turns out aren't that bad) and a charitable effort gone wrong (although that worked out in the end, too). It just hasn't been a smooth ride up to release.
PC Gamer tested Steam Family Sharing on our own and confirmed Shadow of War is not supported—it shows a "Purchase" button where games that support Family Sharing show "Play." We also noticed that Quake Champions and Arma 3 (of the 42 games we had installed) didn't seem to support Family Sharing.
I reached out to Warner Bros. for more information, and will update if I receive a reply. For now, if this is relevant to your purchasing decision, consider yourself warned. Either way, it's out today, and here's our review.