Rating: 4.0/5 ⭐⭐⭐⭐
Spice Rating: 🔥🔥🔥🔥 (4/5 - Steamy)
Plot Rating: 📚📚📚⭐ (3.5/5 - Quick & Engaging)
Let's address the elephant in the room right away: this is a stepsibling romance. Not blood-related, but still sharing awkward family dinners and a last name. If that's not your cup of tea, you can stop reading now and go find something less morally ambiguous. But if you're still here, buckle up, because Lauren Biel's "Last Mistake" is a wild, spicy ride through forbidden territory that'll have you questioning your own moral compass while simultaneously fanning yourself.
This novella is what happens when you take the masked man fantasy, throw in some stepsibling taboo, add a protective hero with a pierced... well, you know... and wrap it all up in 109 pages of pure, unapologetic indulgence. It's the literary equivalent of eating an entire pint of ice cream in one sitting—you know you probably shouldn't, but damn if it doesn't feel good in the moment.
Plot Summary: Identity Crisis Meets Forbidden Attraction
Mason and Harley are stepsiblings who share a house but not much else—certainly not affection. Harley despises Mason with the kind of passionate hatred that only comes from believing someone you once trusted committed an unforgivable act. Years ago, Mason was accused of a crime that landed him in juvie, and Harley, being the stubborn, judgmental person she is, never bothered to hear his side of the story. She just assumed the worst and has been treating him like garbage ever since.
But here's the twist: Mason was innocent. The real perpetrator is still out there, and now they're back with revenge on their mind—specifically, revenge that involves hurting Harley. Mason, being the protective stepbrother he is (despite Harley's constant hostility), decides to go undercover to keep her safe. He dons a mask, creates an alter ego named "Guy," and starts showing up at the college parties Harley attends.
The plan is simple: protect Harley from a distance, make sure nothing bad happens to her, and maintain his cover. What Mason doesn't expect is for Harley to fall for Guy—the masked stranger who keeps appearing in her life with perfect timing and an air of mystery. For the first time in years, Harley lets her guard down, and she starts getting to know the real Mason, even if she doesn't realize it's him.
As Guy, Mason can be himself without the weight of their shared history. He can flirt with Harley, protect her, and show her who he really is beneath the accusations and assumptions. They exchange phone numbers (his from a burner app, naturally), text constantly, and the chemistry between them is absolutely electric. The tension builds as Harley becomes more and more attracted to this mysterious masked man, while Mason struggles with the knowledge that she's falling for him—just not the version of him she thinks she hates.
The inevitable revelation comes in the most deliciously awkward way possible (seriously, the scene where Harley discovers Guy is actually Mason is chef's kiss), and then we get to watch these two navigate the aftermath of forbidden attraction, family dynamics, and the question of whether love can overcome years of misunderstanding and resentment.
Characters: The Good, The Stubborn, and The Pierced
Mason—Our hero is the definition of a protective, misunderstood bad boy with a heart of gold. He spent time in juvie for a crime he didn't commit, and instead of becoming bitter, he's channeled his energy into protecting the one person who refuses to believe in his innocence: his stepsister.
What makes Mason work as a character is his duality. As himself, he's guarded and resigned to being the villain in her story. As Guy, he's confident, flirtatious, and free to be the person he really is without the baggage. The pierced anatomy is just a bonus that adds to his bad-boy appeal, and his dirty talk game is absolutely on point.
The only real issue with Mason is that he's almost too perfect. He's protective without being controlling, patient without being a doormat, and willing to sacrifice his own happiness for Harley's safety. It's swoon-worthy, but it also makes him feel a bit one-dimensional at times.
Harley—Oh, Harley. Sweet, stubborn, infuriating Harley. She's the FMC who will test your patience more than once. Harley is a virgin who has spent years hating Mason based on assumptions rather than facts. She never once asked for his side of the story and has been treating him like dirt for years.
When she meets Guy, she's immediately drawn to him—the mystery, the danger, the way he makes her feel safe and desired. The problem is that her stubbornness and refusal to communicate make her frustrating as a character. Multiple reviewers have called her "annoying," "a twat," and "naive," and honestly, they're not wrong.
That said, Harley does have her moments. Her journey from hatred to understanding to love is compelling, even if it's rushed. She's young, inexperienced, and has been holding onto anger for so long that it's become part of her identity. Watching her let go of that anger is satisfying, even if you want to shake her a few times along the way.
Guy (Mason's Alter Ego)—Guy deserves his own mention because he's essentially a separate character. He's the version of Mason that gets to exist without the weight of their shared history. Guy is confident, mysterious, and unapologetically sexual. The mask gives him freedom, and that freedom is intoxicating for both him and Harley.
The Good Stuff: Actual Quotes
"You're my forbidden fruit, sweet girl.... I'm trying so hard not to take another bite of you."
This quote perfectly encapsulates the central tension of the book. Mason knows Harley is off-limits—she's his stepsister, she hates him, and pursuing her is a terrible idea. But the attraction is undeniable, and the forbidden nature of their relationship only makes it more intense. The "sweet girl" nickname is used throughout the book and becomes a signature part of their dynamic.
"I had made a lot of mistakes in my life, but I wanted her to be the last. My last mistake."
This is the quote that gives the book its title, and it's both romantic and tragic. Mason sees loving Harley as a mistake—something that will inevitably blow up in his face—but he's willing to make that mistake anyway. It speaks to the self-sacrificing nature of his character and the depth of his feelings for her.
These quotes showcase Lauren Biel's ability to write emotionally charged dialogue that captures the forbidden, desperate nature of Mason and Harley's relationship. The language is simple but effective, conveying both desire and the awareness that what they're doing is wrong by societal standards.
Trigger Warnings: Proceed with Caution
Lauren Biel herself describes this as a "lighter" book compared to her usual work, but it still comes with important trigger warnings:
- Stepsiblings/Forbidden Romance - This is the central premise, so if this is a hard no for you, skip this book
- Mention of Sexual Assault (off-page) - Referenced in Mason's backstory
- Attempted Sexual Assault (stopped quickly) - Happens during the story but is interrupted
- Hidden Identity/Deception - Mason deceives Harley about his identity as Guy
- Underage Drinking/Drug Use - College party scenes
- Past Incarceration - Mason's time in juvie is discussed
The author is upfront about these triggers, which is appreciated. While this is definitely "lighter" than some of Biel's other work, it's still not for everyone.
Tropes: A Forbidden Feast
This novella is packed with tropes that dark romance readers will devour:
Stepsiblings - The foundation of the entire story. They're not blood-related, but they share parents through marriage, making their attraction taboo.
Masked Man - Mason's Guy persona involves wearing a mask, playing into the mystery and fantasy elements that make the relationship possible.
Hidden Identity - The entire premise revolves around Mason hiding his true identity from Harley while getting close to her as Guy.
Enemies to Lovers - Harley hates Mason at the beginning, and watching that hatred transform into love is a key part of the story.
Protective Hero - Mason is constantly watching over Harley, protecting her from threats she doesn't even know exist.
Virgin FMC - Harley is inexperienced, which adds to the forbidden nature of their relationship and allows for some teaching moments.
Pierced MMC - Mason has a piercing in a very specific place, which is mentioned multiple times and plays into the spice factor.
Secret Relationship - Once they get together, they have to hide their relationship from their parents and the world.
Touch Her and Die - Mason is fiercely protective and doesn't tolerate anyone threatening or hurting Harley.
What Works: The Spicy Goodness
The Spice - Let's be real: the spice in this book is excellent. Lauren Biel knows how to write steamy scenes that are both hot and emotionally charged. The chemistry between Mason and Harley is palpable, and the scenes are frequent enough to keep things interesting. The pierced anatomy adds an extra layer of intrigue, and the dirty talk is top-tier.
The Pacing - At 109 pages, this novella moves quickly. There's no filler, no unnecessary subplots—just a straightforward story that gets to the point. You can easily finish it in one sitting (and many reviewers did exactly that).
The Mask Element - The masked man trope is executed well here. It's not just a gimmick; it serves a real purpose. The mask allows Mason to be vulnerable with Harley in a way he couldn't be as himself, creating delicious tension when Harley is attracted to Guy without knowing he's Mason.
The Dual Identity - Watching Mason navigate being both himself and Guy is fascinating. The way he uses the Guy persona to show Harley who he really is—his humor, his protectiveness, his desire—adds depth to what could have been a simple forbidden romance.
What Doesn't Work: The Frustrations
Harley's Character - This is the biggest complaint from readers, and it's valid. Harley is stubborn to the point of being irrational. She never once asks Mason for his side of the story and treats him terribly for years based on assumptions. While her eventual character growth is satisfying, getting there is frustrating.
The Length - While the novella format works for a quick read, it also means character development and emotional depth are sacrificed. We don't get enough time to really understand Harley's motivations or to see Mason's trauma fully explored.
The Resolution - The ending feels rushed. After years of hatred and misunderstanding, Harley's acceptance happens very quickly. While it's satisfying, it doesn't feel entirely earned given how stubborn she's been.
The Taboo Element - The stepsibling aspect will be a dealbreaker for some readers. While they're not blood-related, they do share parents and a home, which makes the relationship uncomfortable for readers who aren't into this particular taboo.
The Verdict: A Guilty Pleasure Worth Taking
"Last Mistake" is exactly what it promises to be: a quick, spicy, forbidden romance that doesn't apologize for what it is. It's not trying to be a deep, literary exploration of complex relationships—it's a fantasy, a guilty pleasure, a "what if" scenario played out in the safest possible way (fiction).
The 4.0/5 rating reflects a book that delivers on its promises but has some notable flaws. The spice is excellent, the pacing is quick, and the forbidden nature of the relationship creates genuine tension. However, Harley's character can be frustrating, the length limits character development, and the resolution feels somewhat rushed.
The spice rating of 4/5 is well-deserved. The scenes are hot, frequent, and well-written, with good chemistry and creative use of the masked man element. The pierced anatomy adds an extra layer of intrigue, and the dirty talk is on point. It's not quite a 5/5 because there could have been more variety in the scenes, but what's there is definitely satisfying.
The plot rating of 3.5/5 reflects a straightforward story that works but doesn't break new ground. The hidden identity plot is executed well, and the protective hero angle is compelling, but the overall story is fairly predictable. The novella format means there's not much room for complex plotting or surprising twists, but what's there is solid and engaging.
Who Should Read This:
- Fans of forbidden romance who aren't squeamish about the stepsibling trope
- Readers who love masked man fantasies
- Anyone looking for a quick, spicy read
- Lauren Biel fans who want a "lighter" entry point into her work
Who Should Skip This:
- Anyone uncomfortable with stepsibling relationships
- Readers who need fully developed, complex characters
- Those who prefer slow-burn romance
- Anyone looking for a plot-heavy story with lots of twists
Bottom Line: "Last Mistake" is a fun, spicy romp through forbidden territory that knows exactly what it is and delivers accordingly. It's not perfect—Harley will test your patience, and you'll wish for more depth—but it's an enjoyable guilty pleasure that's perfect for when you want something quick, hot, and unapologetically taboo. Just maybe don't read it at your next family dinner.
And seriously, if your stepbrother starts wearing a mask and showing up at parties, maybe ask some questions before things get complicated. Just saying.
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