Unless you are a Star Trek nut, I can’t recommend the book Redshirts.
It did win the 2013 Hugo Award, so SciFi fans do like it.
As usual with Scalzi, the plot is ingenious.
In a TV series like Star Trek — called the Intrepid — the fictional universe is actually real. Characters from the TV show travel back in time (like Star Trek) and try to get the show cancelled.
Once there, they meet their actor doubles and realize that they are exact doppelgängers.
This book didn’t win me over in any way.
Of course a “redshirt” is a stock character in fiction who dies soon after being introduced. The term originates from the original Star Trek (NBC, 1966–69) in which the red-shirted security personnel frequently die during episodes.