Achlys Books in Order

Erin Bowman’s Achlys books, Contagion and Immunity, sit where science fiction, thriller, and horror overlap. The story starts with a distress call from a distant work site and a rescue mission that should be routine. Instead, the crew lands on Achlys and finds bodies, abandoned gear, and the unmistakable sense that whatever happened there is not finished.

At the center are young characters who are smart enough to know they are in trouble, but not powerful enough to control the system around them. Thea Sadik is an intern working under microbiologist Lisbeth Tarlow. Nova Singh is a pilot trying to keep people moving when fear starts cracking the group apart. By the time the duology moves into Immunity, survivors including Coen are forced to think beyond simple escape and toward stopping something much larger.

It gets claustrophobic fast.

Achlys matters because the setting keeps tightening the screws. Bowman uses remote drilling sites, damaged outposts, failing communications, harsh terrain, and sealed ships to make every mistake feel expensive. There is nowhere easy to run, and help is never close. That isolation gives the books their strongest tension, because even capable people have to make decisions with limited time, incomplete information, and no guarantee that the person next to them is telling the truth.

The series is also interested in what fear does to a group. Infection is only one problem. So are bad orders, secrecy, corporate priorities, and the way people start hiding things when trust breaks down. Nova is trying to keep the mission moving. Thea is trying to understand what they are really facing. Other crew members are carrying their own motives and panic into every scene. Survival depends as much on judgment and honesty as it does on weapons or luck.

In Immunity, the scope widens without losing that pressure. The survivors learn that rescue does not automatically mean safety, and the threat they faced on Achlys may be turned into something even worse. The stakes shift from one nightmare on one planet to a possible political disaster, but the focus stays personal. These are still books about tired, cornered young people trying to do the right thing while the adults in power make everything harder.

These are not slow, idea-heavy space operas. They move. The horror comes from motion, locked doors, blood where it should not be, a crewmate acting strangely, and a warning that arrives too late. If you like sci-fi with a strong cast, a dangerous mystery, and very little breathing room, this pair of books is a sharp place to start.