He’s her boss. She’s his assistant. But what they’re building is worth the trouble.
Billionaire heartthrob. Unserious playboy. It’s nothing Mason Heart hasn’t heard before. It’s an act he’s been all too willing to play, keeping his heart safe from those who would use it for his family name and all that comes with it. But something’s changed. Seeing his older brothers fall in love has made him realise he wants something serious—a family of his own.
Enter Callie Moore. She’s the most beautiful woman he’s ever seen, and the one he cannot have. Despite how much he likes her sense of humour, creativity, and self, she’s his new assistant and strictly off-limits.
Callie Moore moved to Heart City with one goal: to make a better life for her daughter than she ever had growing up, away from her toxic ex and her parents’ tumultuous relationship.
Navie is her number one priority, but Callie can’t help the lingering thought, deep down, that she wishes someone would choose her and love her with their whole heart. While Mason Heart, her new boss, is undeniably gorgeous, he’s also a playboy, having slept his way through Heart City. But the more she gets to know him, the more she realises he’s not who he pretends to be. He’s gentle, kind, and encourages her independence and creativity in a way no one ever has. And he loves Navie, too.
With Mason’s new home renovation keeping them both busy and in professional proximity, all the reasons to keep their distance fade, and Callie and Mason can’t resist the undeniable pull between them. And as they fight their way through everything that tries to keep them apart, they realise what they’re building is worth the trouble.
(ARC Review)
Mason Heart has me in a chokehold, and I don’t know that I’m okay.
This man practically falls in love at first sight. Mason has never been in love, never wanted to settle down, and has spent years happily playing into his reputation as the unserious billionaire playboy. Then he looks into Callie Moore’s gorgeous blue eyes and suddenly it’s like every part of him recognizes exactly what he’s been waiting for.
And once Mason decides Callie is his forever? That man is GONE.
Callie’s not just the girl of my dreams, she’s the girl that rewrites my world.
The yearning. The way he pays attention to absolutely everything she says. The fact that he renovates his house based on exactly how she describes her dream home, quietly creating a space for both her and her four-month-old daughter, Navie, before Callie can even imagine that future for herself. Mason doesn’t just want Callie. He wants her life. He wants the baby, the chaos, the responsibilities, the everyday moments—he wants all of it.
Watching him fall for Navie right alongside her mother might have been one of my favorite parts of the entire story. There’s no hesitation about Callie being a package deal. Navie simply becomes another person Mason loves, protects, and makes room for. The ease with which the three of them begin to feel like a family made my heart ridiculously happy.
When I imagine my future, it’s not just Callie I see. It’s a thousand different moments with Navie, too.
But what really got me about Mason was that his need to take care of Callie never came at the expense of her independence.
Callie has spent her life being disappointed by the men who were supposed to love her. Her father. Her ex. The people who should have taught her that love was safe instead taught her that people leave. So how is she supposed to believe this man, especially a man with Mason’s reputation, when he tells her he wants forever?
There’s a vulnerability underneath Callie’s strength that I loved. She moved to Heart City determined to create stability for herself and Navie. She wants to stand on her own. She wants to build a life she can be proud of. And Mason never tries to take that away from her.
Instead, he builds her confidence. He encourages her creativity. He gives her room to show up for herself and fight her own battles while making damn sure she knows he’ll be standing beside her when she does. If there’s something he can do to make Callie’s life easier, he simply does it. No questions. No fanfare. No expectation of praise.
He just loves her.
And for a woman who has learned to expect abandonment, Mason slowly shows her that real love stays.
“You falling for me, Heartthrob?”
“Since the moment I saw you.”
THAT was the part of their relationship that got me.
Of course, emotional support is certainly not the only thing Mason Heart is bringing to this relationship because GOOD LORD, THE MAN.
The pierced cock. His enthusiastic appreciation for Callie’s postpartum body, including her C-section scar. The mirror scene. The phone call with the ex. His complete and utter devotion to her pleasure. Mason might be one of the sweetest men in the Heart City universe, but apparently all that golden-retriever energy disappears the second the bedroom door closes.
The spice was SPICING.
“So desperate and messy for me. Tell me why?”
“Because…”
“Why, Callie Baby?”
“Because you’re such a good boy when you f*ck me.”
And somehow, even the physical side of their relationship reinforces everything I loved about them emotionally. Callie has spent so much time questioning her worth, and Mason looks at this woman like there is absolutely nothing about her he wouldn’t worship. He makes her feel beautiful, wanted, capable, and treasured without ever making her feel like she needs him in order to be whole.
Then there’s the rest of the Heart City crew.
The sibling chaos remains one of my favorite parts of this series, and Mason’s personality makes those interactions even better. The friendships, the family dynamics, the banter, and the little glimpses of relationships still to come made Heart City feel as lively and interconnected as ever. I also really enjoyed the mystery subplot woven through the romance. It added another layer to the story without overwhelming what I was really here for: watching Mason become completely and irrevocably obsessed with Callie Moore.
And the letters? The surprise? Mason taking everything Callie had unknowingly told him she wanted and turning it into something tangible?
“You wrote me love letters? When did you do this?”
“While I was falling in love with you.”
Sir.
Mason may have started this book thinking he was finally ready for something serious, but I don’t think he could have anticipated just how completely Callie and Navie would become his entire world. He didn’t simply fall in love with a woman. He fell in love with the life they could build together, and then he started building it.
If I could have written my own perfect man, apparently I would have written Mason Heart: filthy, funny, ridiculously attentive, completely down bad, protective without being controlling, and absolutely determined to make the woman he loves understand that she is worth choosing every single day.
Callie needed someone who would stay.
Mason needed someone who made him finally want forever.
And watching them find both in each other made Untroubled Heart such a beautiful ending to the Heart brothers’ stories.
Release Date: August 31st, 2026
Thank you to Emme Goode for the ARC read!