This is a standalone novel; from the notes in the book, it was expanded from an award-winning novelette, but the new material is a complete narrative, and the two narratives are interwoven fairly well. Even if the old material is exactly the same as the earlier publication, well over half of the book is new material, and there's reason to read it (although the really important plot will have been spoiled).
This is harder SF than most of what's being written these days. We have speculation about physics and cosmology that makes as much scientific sense (to me, anyway) as some stuff I read on news web sites about what the real physicists are up to. Of course, being a novel, it doesn't have the math, but I wouldn't be able to follow the math if it did. We also have some interesting, if hard to swallow, speculation about making history into a rigorous discipline, backed up with very timely stuff about the nature of historical research in the age of teh Intarwebz. The book is mainly about one of the main themes of SF and handles that theme convincingly. Really, the only thing I don't like is that the part of the story that's set in the past is set in a period that don't really enjoy visiting, and I'll rant about that inside the cut because it's a minor spoiler.
Tons of stuff to think about, and a good enough story that I can definitely recommend it. 9 out of 10.
**** SPOILERS ****
First, the spoilery kvetching. The in-the-past part of the story happens at the time of the Black Death in Europe. I don't like reading about all the people I've come to know all dying of one of the scariest and ickiest plagues ever imagined. It's just one of those areas that, once I know a little about it, I'd rather skip over rehearsing the details. Even the most masterful writer can't make a story there appealing, and even when his whole plot really does depend on setting it at that time, it seems like a bit of cliche cop-out. Balanced against these bad feelings are the fact that I got to learn a bunch of stuff about Europe just before the Black Death that was genuinely fascinating. If I can believe Flynn, a first go-round of the Renaissance, even better than the one we remember today, was snuffed out. I never realized that Europe in the 1340s was such a hopping place, intellectually. A generation or two later, and we might very well have figured out enough about disease that the plague could have been mitigated, and wouldn't that be a great place to start an alternate history?
**** PLOT SUMMARY ****
There are two different sets of characters, one in 1348 and one in the present day. Rather than try to summarize cutting from one to the other, I'll summarize the medieval story and then the modern day one.
Father Dietrich is a really smart fellow; he studied in Paris with the best minds of Europe, including William of Occam. Then, through some twists that weren't clearly explained (maybe I forgot a bit or two), he was a leader of a mob of religious nutcases who perpetrated some major atrocities. In the book, he's received his own and God's tentative forgiveness, partly achieved by rescuing Theresia, his adopted daughter, but the world's forgiveness is much less certain, so he's in hiding as the parish priest in the Bavarian village of Oberhochwald. One strange morning, there's apparently an enormous electrical field over everything. Metal objects deliver shocks, there's a huge explosion, a fire starts. And then things seem to settle back to normal, until Dietrich finds the spaceship in the woods. The aliens aboard somewhat resemble giant grasshoppers. He calls them Krenken. Eventually Dietrich establishes communication, much aided by the ship's computer and a good supply of radio headsets. The village knows there's somebody in the woods, but they manage to maintain the fiction that it's a group of lepers for a long time. The Krenken are trying to repair their ship but don't really have the tools. They have a little hope if they can get some copper wire made. Dietrich travels to Freiburg where there is a real smith, with an ingot of copper, and stays until the wire is made. Then he gets kidnapped by von Falkenstein, a genuine robber baron, and rescued by the Krenken with explosives and some kind of technological flight. Eventually the Krenken agreen to help take out the castle, to get the wire back. The Krenken are dying because there's an amino acid vital to their chemistry that they can't find in any earthly food. Their doctor kills himself so that they can use his body as a source. The scientists have managed to finish their jury-rigged patch, but they're afraid that it will get them into hypospace but not back, and a few stay back. The Krenken identify which of the villagers have the plague (even without symptoms) and a party, led by Joachim the underpriest, who believed until the end that the Krenken were demons and the village was being tested to see if they could be converted. All who remain in the village die, humans of plague, aliens of amino acid deficiency.
In the present day, Tom is a cliologist, a practitioner of the new science of history. He's onto some cliological pattern that says there should be a village at a certain spot in Germany, and there isn't. Eifelheim is just a void on the map. Eventually, he discovers that there used to be a village there, called Oberhochwald, that was destroyed in the Black Death. Careful research digs up tantalizing clues, and then suddenly his girlfriend Sharon looks at the strange illumination from one of the more interesting manuscripts and recognizes that it's a circuit diagram. They go to Germany and succeed in finding the grave of Johann von Sterne, with a blatantly alien body mostly undecomposed in it. With the clue of the circuit, and more vitally the knowledge that it's possible, it's implied at the end of the book that Sharon will discover the secret of transitioning through the "hypospace" of the hidden dimensions inside the four-dimensional bubble in twelve-dimensional space that we call the universe, and return the bodies of the ill-fated expedition.