Edenborn prominently features a child named Haji of Muslim background who is also a Sufi. He struggles to find God’s will in a complicated future world.
[Thanks to John W. for the synopsis and to Jennifer C. for the pointer]

Here is an excerpt from a review at Fantasy and Science Fiction.

Idlewild gave us an amnesiac adolescent who discovers he’s living in a world of immersive virtual reality (IVR) created to raise him and the handful of other kids he knows because the world has been wiped out by a disease called the Black Ep. …. One of them, Isaac, disagrees with the other two on a fundamental principle: He believes they should bring back unmodified humans and use the technology to find a cure for Black Ep. …. Few of these characters are especially interesting or even convincing, except for Haji, one of Isaac’s unmodified children. Isaac has raised his kids in his Sufi Islamic faith, and Haji’s youthful struggle to discern the will of God in the plague-haunted world is not only endearing and poignant, but constitutes the most unusual element in Edenborn. It’s rare to find sympathetic treatments of religious faith in sf, and these days even rarer to find Islam portrayed anywhere as anything but a jihadist’s delusion. Haji’s presence elevates what is otherwise a moderately entertaining but thoroughly derivative book.