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Revenge and fate come together in the seventh installment of the Pyte/Sentinel Series as New York Times bestselling author R.L. Mathewson tells the story of how one of the deadliest shifters in our world is finally brought to his knees.

He couldn’t kill her.

Their mating mark would never allow it, but it would allow him to walk away and never look back. But that wasn’t a choice, not when Kale knew just how dangerous his mate could become if she ever lost control. His plan is simple, keep her safe, out of his way, and focus on the only thing that mattered. He didn’t need her, didn’t want her, and…

He couldn’t stop thinking about her. 

No matter how many times Kale tries, he can’t stay away from her and god, does he try. With a bounty on his head and shifters, demons, and vampires doing everything they could to find him, the last thing that Kale needs is to fall in love with his mate.

This wasn’t supposed to happen.

No one was supposed to find her. At least, that was the plan, but somehow the incredibly sexy shifter that loved to glare had found her and now…

She was finally where she belonged.

The only problem was, Ashley had no idea why, but she wasn’t going to complain. Not when things were finally making sense. What she was going to do was pretend that the shifter that hated her didn’t make her want things that she couldn’t have. She just needed to lay low, pretend that she had no idea why anyone would be after her, and hope that her secrets didn’t tear them apart.

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To Download a sample of Unstoppable, click here.


Reviews for Unstoppable

A suspenseful story with a paranormal theme that was riveting to read. I especially loved the supporting cast of characters who were added seamlessly into the storyline creating depth and detail that made the book even more enjoyable. I can’t wait to the next book. I loved their story.


I’d give Unstoppable more ⭐’s if they had them.
I absolutely loved Kale and Ashley. This story grabbed my attention from the very beginning.
I’ve wanted his story since Without Regret.
Im not giving any details because whatever I say would be a spoiler.
I will say that R.L. brings humor and sparks that touch the soul to everything she writes. No matter what genre it happens to be. She’s my unicorn author.


I can not get enough of this series! I dread finishing the books in the series because they give me the escape I need from everything and I love all the characters in them. Kale is my favorite ever since he made his appearance in book 2. I have waited for this book for so long and I got more than I bargained for! R.l Mathewson gave us a look into Kale and what he has been through and done in his long life and made me love him even more than before. I can’t wait for the next in the series!!!

–Amazon Customer

R.L. Mathewson you f#%$% rock! Ok people hear me out…everything R.L. Mathewson writes is amazing because her writing style is unique from all the other romance authors out there. Not only are her stories hot and steamy but they have an element of humor that makes you just want to sit back and devour the book in one sitting. Before you even know it you are on the last chapter and wishing that the next book in the series is not far behind. I LOVED THIS BOOK!

–Maria AddictedToLove

I have been waiting for Kales book for what feels like forever, and it didn’t disappoint! I own every single book by R.L. And she hasn’t let me down yet! If you haven’t read the “Neighbor From Hell” series yet, I strongly recommend! You will laugh, swoon, and fall madly in love with the Bradford men and women! Again, I loved this book, I’m only sad it ended! Can’t wait for the next installment to this series!


I have been waiting for this book for a while now and damn was it worth the wait! R.L Mathewson always keeps me laughing but at the same time I get choked up. So many emotions in this book. I couldn’t put it down. This is definitely now a favorite in this series. Now I’m greedy for more. I’m ready for Jill and Joshua… please and thank you!

–Rachel J Eisele

I love everything about this book. RL did an amazing job at telling Kales and Ashley’s story but also including all of the other characters and their storylines into this book. This book has a lot of “set ups” for future books and I cannot wait! Please check out the other books in this series, including the Neighbors from Hell and Anger Management series.

–Samantha Bagley

MS Matheson once again has gone above and beyond. Kale finally meets his mate. I tried to only read a few chapters at a time but devoured the book in a day. I do advise you read all the books before, in order, because everyone shows up from previous stories. Absolutely fantastic!

–Kindle Customer

Just when you think that Ms. Mathewson can’t make you fall in love with one more of her super-hot Alpha males, she does it again…
Kale’s book took me on a journey of redemption and hope and made me believe that love truly conquers all!
It was a brilliant book and I’ll be re-reading soon!


I swore I wasn’t going to read it in one sitting. That was lie I couldn’t stop once I started. Kale just sucks you in. This book was so worth the wait. I cannot wait for the next one.


This was such a good book. I love this series and repeatedly asked myself, “why is R.L. Doing this to me.” LOL. I couldn’t stop reading. I can’t wait for the next book in the series.

–Tiffany Brewster

Print Excerpt

“I-I would never hurt anyone,” Ashley mumbled absently as she stumbled back.

“And we’ll never find out if that’s true,” Kale said as he continued following her, noting the nervous glances that she kept sending the door and the way that she winced with every sound barely above a whisper.

“Why haven’t you slipped into bloodlust?” Kale wondered, following her as he noted that she’d lost weight, the way that she’d gone pale when he bit into his wrist, the fact that she wasn’t running for the front door, and how she noticeably struggled to stop looking at the blood dripping down his hand.

“I don’t know,” Ashley said, licking her lips nervously as she continued backing away from him.

“You took your transition well,” Kale pointed out, watching her closely.

She snorted at that. “Of course, I took it well. Why wouldn’t I? I looked like a little girl before this.”

“I’m not talking about that,” he said, thinking about her reaction the moment that she’d realized she wasn’t human, the way she’d reacted when her eyes turned red and she spotted her fangs in the mirror.

Her reaction had been more curious than surprised. She hadn’t panicked, freaked out, screamed, cried, or reacted like a woman who had no idea about all those things that go bump in the night should have. The same could be said for when Jacob had been forced to shift in front of her to fix his broken arm. She’d been terrified. There was no question about that, but there had also been a haunted look in her eye as though she’d seen it before. She also hadn’t argued or flipped out over the fact that she needed to drink blood, something that she definitely should have been upset about. Instead, she’d resigned herself to the fact that she required blood for the rest of her life without question, leaving him with more questions.

“You’re not telling me something,” Kale said as he stalked her around the small bedroom.

Licking her lips nervously, Ashley said, “Neither are you,” as she continued to move away from him.

“And I’m not going to,” Kale murmured quietly as he watched her bump into the bed only to quickly climb over it with a curse so that she could put the bed between them.

“Then neither am I,” she said with a firm nod, trying to sound tough, but the way that she worried her bottom lip killed the effect, making her look fucking adorable.

Nodding, Kale shifted to the right and began moving around the bed. “I know one thing.”

“What’s that?” Ashley asked, stumbling back away from the bed as she looked around frantically for somewhere to run.

“You’ve been around shifters before,” Kale said, watching as she quickly closed her mouth into a firm line, it was a small move, but a telling one.

“Which Pack?” he asked, moving closer as he scented the air, looking for any trace of shifter blood on her, but he couldn’t scent any. The only thing that he could smell was the telltale scent of Pyte and fear as she backed up towards the bedroom door. He followed her, refusing to let her go as he watched her, knowing that he was right.

“What’s going on?” Jacob asked as he walked back inside.

“Ashley was just about to tell me,” Kale said, watching her struggling not to panic as she reached down and yanked her shorts back up while she continued backing up, refusing to take her eyes off him.

Smart girl, Kale thought as he allowed his fangs to slide down, watching as her eyes took in the move and had to wonder how she’d managed to escape. She’d been trapped in the body of a child, weak, and easily controlled.

“Did the Pack have an Alpha?” Kale asked, noting the way that her jaw clenched in response.

He could understand a Pack without an Alpha fucking up and letting her escape, but an Alpha…

Would have torn her throat out to make sure that another Pack couldn’t get their hands on her. It left him with more questions that unfortunately for her, he didn’t have time for.

Deciding that they’d played this game long enough, Kale grabbed Ashley and shoved her against the wall. Before she could react, he had his fangs pressed against her throat in warning. As soon as she felt the sharp tips pressed against her skin, she went still as he forced himself to ignore just how good she smelled and released a warning growl, one that had her swallowing hard and her heart racing. He waited for the scent of fear to hit him before he pulled back just enough so that he could speak without risking breaking her skin, knowing just how dangerous her blood was.

“Have you ever seen someone’s throat ripped out?” Kale asked as he leaned back in and carefully ran the tips of his fangs over her soft skin.

“Y-yes,” came the weakly mumbled answer that had him pulling back.

“Who?” Kale asked, watching as her expression grew sad.

“My mother.”

New York Times Bestselling author, R.L. Mathewson was born in Massachusetts. She’s known for her humor, quick wit and ability to write relatable characters. She currently has several paranormal and contemporary romance series published including the Neighbor from Hell series.

Growing up, R.L. Mathewson was a painfully shy bookworm. After high school, she attended college, worked as a bellhop, fast food cook, and a museum worker until she decided to take an EMT course. Working as an EMT helped her get over her shyness as well as left her with some fond memories and some rather disturbing ones that from time to time show up in one of her books.

Today, R.L. Mathewson is the single mother of two children that keep her on her toes. She has a bit of a romance novel addiction as well as a major hot chocolate addiction and on a perfect day, she combines the two.

In 2019/2020, R.L. Mathewson will be publishing Devastated, the first Anger Management novel, Tall, Dark & Furious, the 6th installment to the Pyte/Sentinel series, Irresistible, the long anticipated novel for the Neighbor from Hell Series as well as many more books throughout the year, paranormals, contemporaries, and YAs.

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