Sigma Force vs The NUMA Files
Two thriller series side by side, straight from the catalog data: The NUMA Files is the longer series (15 books vs 14 books); Sigma Force is the more recent one, starting in 2004. There's no wrong answer — pick the shape that fits your reading appetite, and Shelfmark will keep your place in either (no account needed).
| Statistic | Sigma Force | The NUMA Files |
|---|---|---|
| Author | James Rollins | Clive Cussler |
| Books | 14 | 15 |
| Published | 2004–2019 | 1999–2017 |
| Books per year | 0.9 | 0.8 |
| Start with | Sandstorm (2004) | Serpent (1999) |
| Reading order | Full Sigma Force order → | Full The NUMA Files order → |
Numbers come from the Shelfmark catalog (Wikidata + Open Library). "Books per year" is catalogued books divided by the publication span — a rough cadence, not a quality score.