The Recommended Reading Order
Marko Kloos’s gritty military science fiction series is best experienced in publication order. Because the narrative follows a linear timeline detailing the career of soldier Andrew Grayson, reading the books in the order they were released prevents major spoilers and ensures a smooth character progression. Companion novellas can either be read at their chronological points or saved as supplementary reading after you finish the early books.
Here is the recommended reading path for the entire Frontlines universe:
- Terms of Enlistment (Book 1)
- Lines of Departure (Book 2)
- Lucky Thirteen (Book 2.1 — Companion Novella)
- Measures of Absolution (Book 2.2 — Companion Novella)
- Angles of Attack (Book 3)
- Chains of Command (Book 4)
- Fields of Fire (Book 5)
- Points of Impact (Book 6)
- Orders of Battle (Book 7)
- Centers of Gravity (Book 8)
- Scorpio (Frontlines: Evolution Book 1)
- Corvus (Frontlines: Evolution Book 2)
- Cygnus (Frontlines: Evolution Book 3 — Scheduled for December 2026)
The Andrew Grayson Saga (Books 1 to 8)
The core of Frontlines follows Andrew Grayson, a young man who enlists in the North American Commonwealth's military to escape the bleak, overpopulated welfare tenements of Boston. What starts as a desperate bid for food vouchers and a ticket off Earth quickly turns into an interstellar war for survival against the Lankies — terrifying, near-invincible twenty-meter-tall alien giants who are terraforming and colonizing human outposts.
Terms of Enlistment (2013)
This is where the journey begins. Readers are introduced to Andrew's life in the slums, his basic training, and his first harrowing assignments. The book establishes the gritty, realistic military culture of Kloos's universe, showing that before humanity fought aliens, they were busy fighting each other in urban pacification zones. The story culminates in the disastrous Battle of Detroit, which sets the stage for Andrew's transfer to space-based operations.
Lines of Departure (2014)
Now a seasoned corporal, Andrew is stationed aboard a troop transport ship. The planetary conflicts escalate as the Lankies push deeper into human-controlled space. While grappling with the reality of his dangerous deployment, Andrew must navigate a military system strained to the breaking point by political infighting and logistical failures. This installment highlights the logistical struggles of interstellar warfare and the growing desperation of the human race.
Angles of Attack (2015)
Following the events of the previous book, Earth is cut off, and Andrew finds himself stranded on a remote colony alongside a mix of military survivors. When the Lankies arrive, former adversaries must forge uneasy alliances to mount a desperate defense. The stakes shift from defending abstract national boundaries to preserving the baseline survival of the species.
Chains of Command (2016)
With humanity pushed back to the solar system, Andrew participates in a high-stakes campaign to reclaim lost territory. The novel expands the scope of the war, showcasing massive fleet battles and orbital insertions. It also delves into the political corruption at the highest levels of the Commonwealth, demonstrating that even on the brink of extinction, human greed remains a persistent threat.
Fields of Fire (2017)
Andrew is assigned to a newly formed, elite unit tasked with taking the fight directly to Lanky-occupied worlds. The boots-on-the-ground action is intense as the military tests new tactics and weaponry. The narrative emphasizes the physical and psychological toll that constant combat takes on Andrew and his squadmates.
Points of Impact (2018)
A momentary shift in the war allows Andrew to take a staff position, but peace is short-lived. A new Lanky threat emerges that forces him back into the cockpit. The book explores the evolving nature of the alien threat and the technological arms race humanity is desperately trying to win before their resources run out entirely.
Orders of Battle (2020)
Set after a multi-year time jump, the war has entered a cold phase. Andrew, now an officer, is pulled out of semi-retirement for a secret reconnaissance mission into deep space. The story returns to the series' roots of exploration and mystery, discovering what the Lankies have been building in the quiet years and setting up the final arc of Andrew's story.
Centers of Gravity (2022)
This novel serves as the emotional and narrative conclusion to Andrew Grayson's personal arc. Stranded deep in enemy territory after a jump-space mishap, Andrew and his crew must find a way back home with critical intelligence. It brings closure to his long career as a soldier and his relationship with pilot Halley, leaving the wider universe open for future stories.
Novellas and Companion Stories
Two major side stories enrich the Frontlines universe. While they are not mandatory to understand the main plot, they add depth to secondary characters and world-building.
Lucky Thirteen (2013)
This popular novella is officially designated as Book 2.1. It follows a rookie dropship pilot who is assigned to fly a notorious, seemingly cursed transport vessel named "Lucky 13" that has already lost two previous crews. The story focuses on the bond between the pilot and her machine during a series of dangerous missions. In the original text, the protagonist is Halley (Andrew's partner), serving as a prequel to her role in the main novels. Notably, this story was adapted into a highly acclaimed episode of the Netflix animated anthology series Love, Death & Robots, where the pilot was renamed Lieutenant Colby.
Measures of Absolution (2013)
Designated as Book 2.2, this novella shifts the perspective to Corporal Jackson, Andrew Grayson's former squadmate. It takes place in the immediate, chaotic aftermath of the Battle of Detroit. Jackson searches the ruined housing blocks of the city, trying to understand how a routine pacification mission spiraled into a tactical disaster that cost the Territorial Army control of the region. It is a grim, ground-level study of military pacification and the moral weight of domestic warfare.
The Next Generation: Frontlines: Evolution
Following the conclusion of Andrew Grayson's arc, Marko Kloos launched a spin-off series set in the same universe, focusing on a new cast of characters and a different perspective on the Lanky conflict.
Scorpio (2024)
The first book of the Evolution spin-off shifts focus to Earth colonists who were abandoned on a remote planet during the alien invasion. The narrative follows Alex Archer and her dog, Ash, as they try to survive in underground shelters on a world being slowly terraformed by the Lankies. It swaps the grand military fleet scale for a tense, survival-focused story of civilian resilience.
Corvus (2025)
The second entry in the Evolution series continues Alex's struggles. As the remnants of humanity attempt to regroup and reclaim their lost colony, new conflicts arise between the surviving factions. The book explores the difficulties of rebuilding civilization under the shadow of a persistent alien threat.
Cygnus (Scheduled for December 2026)
The upcoming third book in the spin-off is set to expand the conflict further, detailing the next steps in humanity's evolution as they adapt to a galaxy forever altered by the Lankies.
What to Know Before You Start
Marko Kloos is a former German soldier, and his real-world experience heavily influences the tone of Frontlines. The books avoid overly romanticized views of combat, focusing instead on the mundane details of military life, the frustration of bureaucracy, the tight bonds of squad mates, and the sheer terror of facing an enemy that cannot be reasoned with. It is an action-packed, fast-paced read, but it is grounded in a deep sense of realism that sets it apart from more fantastical space operas.