This is a tough book to review. Especially in the way that I do it. It's like trying to write a review of a joke or a weird YouTube video. Redshirts is first and foremost a farce. It's an idea novel about what happens when the characters of a science fiction television show realize that they are characters in a show. Or maybe it's when people who are just living their lives realize that they are living in a fictionalized world, or at least a world that is being manipulated and influenced by the creators of that show. And made worse by the fact that the show isn't that good.
I think Scalzi is able to move beyond the constraints of the farce for the most part by having characters and situations that actually exist to make the story enjoyable beyond the simple concept of the farce. It's a fun read if you are down with the premise. It's a better read if, like me, you are neck deep in all of the great and terrible science fiction that's been on the air since the late nineties. Indeed, this book reads very much like the meta plot of some of those shows. Redshirts lavishes itself in the flavor of any episode of Stargate SG1 or Voyager where the cast found a premise to time travel to earth of some earlier yet nowish era. They search for the macguffin of the week just long enough to break some fundamental law of the universe and then fix it again before resetting everything back to status quo.
I make the comparison because Scalzi has no problem making it in the book. Redshirts is at all times aware of what it is and what its doing. It's meta, and spiked deep in the vein of the source material it's using for farcical purposes, but assumes that you are in on the joke. I can only hope you haven't gotten deep into this novel without some understanding of the history of bad TV it's standing on. Otherwise you might have a bad time. The whole thing might seem like you are reading bad TV and then wondering to yourself how this much celebrated author got himself into such a hole with the ridiculous premise in the first place.
But if you are in on the joke, Scalzi will take you far with characters you can like and certainly enjoy reading about as they experience the idea that they are characters and being enjoyable become a matter of life and death. Redshirts gets a three out of five.