
Book Review: Sigma
Book details
About the story
MF paranormal military romance sequel: After escaping her ex, Shiloh enters a secret breeding program and finds Sigma—a super-soldier who reveals the truth behind everything that book 1 kept hidden.
Mood
Adventurous & High-Stakes, Dark & Intense
World setting
Genres
Plot pacing
Fast-paced plot
Relationship tropes
Story tropes
Bullying, Abduction / Captivity
Ending type
HEA (Happily Ever After)
Content warnings
Abuse, Attempted murder, Birth‑control non‑consent / Breeding, Blood, Bullying, Death, Graphic language / Profanity, Graphic sexual content, Guns, Injury, Murder, Trafficking, Violence / Brutal injuries
Kinks
Breeding
About the series
Sigma is book #2 of the Alpha series
Depends, in my opinion, this book spoils earlier books in the series, and that’s a deal breaker for me, but it might not be for you.
Book Blurb
Shiloh Green has had the worse luck when it comes to men. For the last seven years she’s been trapped in a relationship with her Kingpin boyfriend. But opportunity to escape comes knocking when a mysterious businessman visits. Now Shiloh is headed to a top-secret military base to be a volunteer breeder for a government experiment. Things go south quickly, and she starts to doubt her decision to leave, until she meets him. Sigma is a quiet recluse who wants nothing to do with the fragile female human, until he realizes she’s his mate. Now Shiloh and Sigma must survive a psycho ex-boyfriend, an enemy from her past, a slighted Rogue, and A mad scientist. Will they make it out the compound alive, or will their love be destroyed.
Shiloh Green has had the worse luck when it comes to men. For the last seven years she’s been trapped in a relationship with her Kingpin boyfriend. But opportunity to escape comes knocking when a mysterious businessman visits. Now Shiloh is headed to a top-secret military base to be a volunteer breeder for a government experiment. Things go south quickly, and she starts to doubt her decision to leave, until she meets him. Sigma is a quiet recluse who wants nothing to do with the fragile female human, until he realizes she’s his mate. Now Shiloh and Sigma must survive a psycho ex-boyfriend, an enemy from her past, a slighted Rogue, and A mad scientist. Will they make it out the compound alive, or will their love be destroyed.
Rating & review
My review
WHAT. A. GOOD. BOOK. Period.
Sigma delivers everything I loved about Alpha—with one major difference: the mystery is gone. And honestly? I loved that too.
Where Alpha kept things deliberately vague, Sigma pulls back the curtain completely. We’re told exactly where the super-soldiers come from, how the experiment works, and what was really happening behind the scenes during the events of Alpha. Reading this felt like seeing the same story from the opposite side of the chessboard—and it was so satisfying.
This book overlaps heavily with Alpha, covering many of the same events, but from Sigma’s perspective. And that’s what makes it such a fun, rewarding read. If Alpha was about the heroine navigating the unknown, Sigma is about understanding the system, the science, and the brutal reality of the super-soldier program.
That said: you need to have read Alpha first. This book assumes you already know and care about that world. And to truly love this one, you also need to be okay with the mystery being fully revealed.
The romance unfolds alongside nonstop external threats: a psychotic ex, enemies from Shiloh’s past, internal betrayals, and a genuinely unhinged scientist pulling strings.
If Alpha made you curious, Sigma gives you answers.
Warning: some injuries and deaths are very very graphic, be careful if you are sensitive to these topics.
The Heroine: Shiloh
Shiloh is a fantastic FMC.
She’s skeptical about love (for very good reasons), mentally tough, resilient, and genuinely smart. Not “strong because the author says so,” but strong in the quiet, believable way—she survives, adapts, and doesn’t trust easily.
It was refreshing to read a heroine who doesn’t romanticize her trauma or instantly fall into blind devotion. She questions everything, including her own decisions, and that made her feel incredibly grounded.
The Hero: Sigma
Sigma is intriguing mostly because of his role within the super-soldier hierarchy and his insight into the experiment itself. Through him, we finally understand the soldiers’ internal dynamics.
As a romance hero, he hits familiar beats: protective, super strong, intelligent, territorial, and jealous. He’s solid, dependable, and very much an alpha-type presence—but his real strength is the perspective he offers rather than reinventing the archetype.
WHAT. A. GOOD. BOOK. Period.
Sigma delivers everything I loved about Alpha—with one major difference: the mystery is gone. And honestly? I loved that too.
Where Alpha kept things deliberately vague, Sigma pulls back the curtain completely. We’re told exactly where the super-soldiers come from, how the experiment works, and what was really happening behind the scenes during the events of Alpha. Reading this felt like seeing the same story from the opposite side of the chessboard—and it was so satisfying.
This book overlaps heavily with Alpha, covering many of the same events, but from Sigma’s perspective. And that’s what makes it such a fun, rewarding read. If Alpha was about the heroine navigating the unknown, Sigma is about understanding the system, the science, and the brutal reality of the super-soldier program.
That said: you need to have read Alpha first. This book assumes you already know and care about that world. And to truly love this one, you also need to be okay with the mystery being fully revealed.
The romance unfolds alongside nonstop external threats: a psychotic ex, enemies from Shiloh’s past, internal betrayals, and a genuinely unhinged scientist pulling strings.
If Alpha made you curious, Sigma gives you answers.
Warning: some injuries and deaths are very very graphic, be careful if you are sensitive to these topics.
The Heroine: Shiloh
Shiloh is a fantastic FMC.
She’s skeptical about love (for very good reasons), mentally tough, resilient, and genuinely smart. Not “strong because the author says so,” but strong in the quiet, believable way—she survives, adapts, and doesn’t trust easily.
It was refreshing to read a heroine who doesn’t romanticize her trauma or instantly fall into blind devotion. She questions everything, including her own decisions, and that made her feel incredibly grounded.
The Hero: Sigma
Sigma is intriguing mostly because of his role within the super-soldier hierarchy and his insight into the experiment itself. Through him, we finally understand the soldiers’ internal dynamics.
As a romance hero, he hits familiar beats: protective, super strong, intelligent, territorial, and jealous. He’s solid, dependable, and very much an alpha-type presence—but his real strength is the perspective he offers rather than reinventing the archetype.
Character & romance details
About the romance
4
Medium burn
MF
Story tropes
Bullying, Abduction / Captivity
Relationship tropes
Kinks
Breeding
About the female lead
Ocupation
None
Virgin protagonist?
No
About the love interest
Ocupation
Warrior, Works for the pack
Virgin love interest?
No
Personality
Jealous, Possessive, Protective
Who will love this book
Sigma is perfect for readers who enjoy:
• Paranormal romance tied to military/super-soldier experiments
• Fated mates with high external stakes
• Strong, skeptical heroines who don’t fall easily
• Alpha heroes who are protective and lethal
• Companion novels that reveal the other side of the story
Books similar to Sigma

Fury
(New Species #1)5
/55
/5Erotic romance: Ellie discovers that her employer creates human–animal hybrids and becomes drawn to Fury, one of its captive subjects. After being freed, Fury battles his attraction to Ellie—but it’s a losing battle.
If you want another super-soldier/human-experiment hero, but one who’s more animal than alien…

Oh hey! I’m Becky, book hugger and the one-woman team behind RBM. I hope my reviews help you find a story you’ll love.

