Sigma Force

About the Sigma Force series

Sigma Force is a covert unit of the U.S. Defense Advanced Research Projects Agency (DARPA), staffed by former special-forces operatives cross-trained as scientists and sent to investigate threats where cutting-edge science and ancient mystery collide. Every novel pairs a real scientific or historical hook — CRISPR gene editing, quantum physics, lost expeditions, ancient plagues, cryptozoology, Norse and biblical lore — with a globe-spanning conspiracy, and James Rollins (a veterinarian by training) grounds even the wildest set pieces in genuine research, laid out in the author's-note that closes every book. The team, led by Commander Gray Pierce, is a true ensemble: linguist Monk Kokkalis, historian Elizabeth 'Seichan' Ang-turned-ally, and a rotating cast of specialists whose personal lives and relationships thread through the mission-of-the-book plots.

Rollins escalates the stakes across the series from single-country crises to genuinely world-ending threats, while keeping each book's central mystery mostly self-contained. Crossover novellas link Sigma Force to Rollins' other series and to Steve Berry's Cotton Malone books, rewarding series-spanning thriller readers. It's a strong pick for fans of Michael Crichton-style science thrillers who also want Indiana-Jones adventure and Dan Brown-style historical conspiracy in the same book.

How to read this series

Publication order, starting with Sandstorm (2004). Team relationships (especially Gray Pierce and Seichan) and a handful of overarching threats develop across the numbered novels, but each book's core science-and-history mystery wraps up on its own, so the series is forgiving to jump into partway through if needed.

A run of digital-only short stories sits between the novels; most are optional character vignettes, though 'The Devil's Bones' is a direct crossover with Steve Berry's Cotton Malone series co-written by both authors, best read once you know both series. New readers wanting the most streamlined path can skip the short stories entirely and read only the 18 numbered novels.