On the face of it Eliza Griswold's The Tenth Parallel: Dispatches from the Fault Line Between Christianity and Islam is a book whose content is summed up accurately by the title. The author recounts her experiences in various African and Asian lands which straddle the tenth parallel north of the equator: Nigeria, Sudan, Somalia, Indonesia, Malaysia, and the Philippines. It is a story told through personal narrative, the author's, and the numerous people who are themselves embedded in larger forces welling up from below and descending from above. One can accurately describe The Tenth Parallel as a travelogue. But it is also a time machine, as Griswold surveys worlds which are a clear simulacrum of those which we know only through works of history; empires of faith, the lands of God's platoons. As such, The Tenth Parallel is also a narrative which describes an alien world of ideas, outside of our conventional categories and classes. Many of the preconceptions and expectations which we bring to the table are "not even wrong" in the lands Griswold traverses, and what has been learned must sometimes be unlearned. This is not Newtonian Mechanics, where a cold and objective eye surveys the terrain and reports back positions and trajectories across space and time. An awareness of the author's viewpoint is critical, while the viewpoint of her sources are plain. Finally, your own presuppositions and experiences as a reader shape the ultimate "take home" message which Eliza Griswold stitches together across her disparate sojourns.