The three stars are for the first two thirds of the book. An interesting overview of early and very early science fiction (Copernicus wrote a scifi novel! Or was it Kepler - dang I returned the book to the library and can't check). The chapters on "The Age of Discovery," "The Mechanical Age," and "The Astounding Age" take us from the demise of Aristotilan world view through Einstein and the Cold War, which is the meat and potatoes of this book.
It's like the authors read all the classics right up to about Dune. The last couple chapters gives up on covering books for the most part, talking about movies instead. I don't mind talking about movies but there were so many books that the authors neglected (and because these were more current many by women authors too). Here's a short list of who I missed: Never Let Me Go by Kazuo Ishiguro in the section about cloning, Beggars in Spain by Nancy Kress in the section about genetic mutation/manipulation, anything by Octavia Butler, Margaret Atwood for either The Handmaid's Tale or Oryx & Crake or Year of the Flood for that matter...