What if aliens came to earth... in 1348? That's the basic premise of Michael Flynn's Eifelheim, though the narrative is split between a modern-day couple, a mathematical historian (Tom) and a theoretical physicist (Sharon) whose work inadvertently dovetail to unlock the mystery posed by certain historical sources, including the apparent disappearance of the German village of Eifelheim. The narrative weaves back and forth between their work and the story of the residents of this village and their "Krenken" visitors, grass-hopper-like aliens. 
 I didn't think that narrative structure worked as well as it could have. Inherent in the Tom/Sharon storyline was an element of mystery, but the story of the villagers made the situation clear early on (which is why I felt no compunction about starting my review by revealing it. Instead, it serves more to justify it: here, it seems to say, is the justification of this novel as science fiction. The Tom/Sharon narrative, we later find, is framed as a story told by a German historian who only enters the story later. It's never entirely clear how the 14th-century villagers' story is framed: we're just told the story, but it seems pretty clear that the historians couldn't have come close to discovering the story in such detail. Instead, we're just given it. That's okay, but it seems odd considering the trouble Flynn went to with the other story. 
 The story of these medieval villagers and stranded aliens has inherent pathos, as the two groups try to overcome obvious--and rather frightening--differences and then again as each group gradually succumbs to starvation (none of the foods they can find give the essential amino acids that the aliens need) or the bubonic plague. We meet some interesting characters, but even so, I felt like the novel would have been improved by deeper characterization. 
 The pace of the novel also seemed slow. In part, this might be blamed on the fact that we listened to this as an audiobook: they're inherently slower and sometimes stylistic issues become more pronounced--things that we would slide right over on the page seem to drag interminably when read aloud. I also wasn't taken with the reader, Anthony Heald. He was particularly annoying when "voicing" Sharon, but on the whole he didn't do much for me. 
 One particular strength of the novel was how well-researched this was. Flynn not only gets the details right, but he also works extremely hard to get inside the mind of medieval man, particular Pastor Dietrich, the protagonist of that storyline. At the same time, Flynn's aliens are no less alien than his medieval men (in fact, with their understanding of science, they're closer to modern men than the 14th-century human beings are, with allowances made for their different evolutionary path. 
 On the whole, it was an enjoyable and interesting read, even given the weaknesses noted.