This was what I came into the thread to recommend, partially because a coworker and I happened to read it at around the same time and while she almost exclusively reads non-fiction and definitely does not read much science fiction, she really enjoyed it. In fact, when talking about a different book chosen for the book club we were both in she said “I don’t know why they keep picking things like [other book]. I would have chosen The Sparrow, it gives you so much to think about!”
It’s also my impression that The Sparrow was marketed as mainstream fiction rather than science fiction. It was in the general fiction section of the public library that I borrowed it from. This was a surprise to me, as I already had a general idea of what the book was about and fully expected that a book that involved travel to another planet and interactions with aliens would be shelved in the science fiction section.
I kind of hate that shelving strategy. Not everyone who’s a mimetic fiction fan does it, but there are plenty of 'em, snotty folks who think mimetic fiction isn’t a genre, it’s just good literature, and that genre literature is by definition bad, so if something genre comes along that gets praised in mainstream publications, it must not be genre.
I would suggest The Plot Against America by Philip Roth. It is a alternate history that imagines a more Nazi Friendly America in the 30s but reads like a literary novel.