According to Wikipedia, a "redshirt" is a stock character in fiction who dies soon after being introduced. The term originates with fans of Star Trek television series (1966–1969), from the red shirts worn by Starfleet security officers who frequently die during episodes. Redshirt deaths are often used to dramatize the potential peril that the main characters face.
Ensign Andrew Dahl is a redshirt, and life couldn’t be better. He's been assigned to the Intrepid, the space fleet's flagship exploration vessel. It’s a prestigious posting, and Andrew is thrilled even more to be assigned to the ship’s Xenobiology laboratory. That is, until Andrew begins to notice that every planetary "away mission" involves some kind of lethal confrontation with alien forces where the ship’s captain and top officers always survive, and at least one low-ranked crew member is always killed.
Life on the ship becomes a matter of avoiding away missions, while at the same time looking busy and staying below the captain's radar. This is partially accomplished with the help of a rogue crew member who lives in the mostly empty corridors below deck. He has the ability to track the officers and warn of their approach. he also has quite an interesting theory as to why things are as they are aboard the Intrepid.
If you are a fan of sci-fi tv, this both irreverent and satirical novel will make you smile with recognition and blow your mind with new, ever complex ideas on the nature of reality.