As I write this, I've piled up a backlog of books to review (because I read while I was sick this week but I didn't review), and I can't connect to the Internet because my phone isn't working. So I can't really say "today's book review". Let's say, rather, that my first deferred book review is
Eifelheim by Michael Flynn.
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.
( spoilery commentary and plot summary )