Book Log 2019 #20: Through Darkest Europe by Harry Turtledove

In this alternative history, changes in both Islamic and Christian theology see the Islamic world become what we would consider the First World, while Europe stagnates and becomes a breeding ground for fundamentalist groups. Into this, a couple of investigators go to Rome to protect an Italian duke and the Pope in the hopes of keeping the violence common in their part of the world from spreading into the Middle East.

There's not much to recommend about this book. The plot isn't particularly interesting, and while the investigative duo are entertaining they don't do that much actual investigating. It's all a bit ham-handed and clumsy. You'd be much better off reading The Years of Rice and Salt by Kim Stanley Robinson (which I apparently read before starting the Book Log), which approaches a similar idea with much better results.