“How can you try to disprove something when it’s standing right there in front of you?”

The Duality Principle

The Duality Principle

She’s a prim-and-proper nerdy girl hiding her reckless desires. He’s a reformed bad boy trying to win her heart.

Gabriella Evans needs to get her head on straight. A PhD candidate, she doesn’t believe she can be both a successful mathematician, and have a life filled with wild passion. 

Connor Starks has spent years breaking laws and breaking hearts, but meeting Gabriella makes him want to prove he’s become a better man. The only problem? She’s driving him out of his mind. 

But Connor will discover his past can’t stay hidden forever, and Gabriella will find out how much fun it is to be bad…

If you’re looking for SCORCHING HOT SEXUAL TENSION that sizzles through the pages, and a sexy as sin story that’s a perfect blend of naughty and nice, grab this standalone romance now!

Warning: This book contains a summer romance, dirty talk, dockside kissing, motorcycles and tattoos. Features a rebellious nerdy girl with an appetite for outdoor sex and light spanking, and a bad boy who’s turned good…or at least he’s trying.

Best Selling Top 100 in Romantic Erotica


Allen’s debut is an utterly charming, delightfully dirty little tale that shouldn’t be missed. Her engagement with her brainy heroine’s secrets is beautifully honest and the addition of a troubled, refreshingly earnest bad boy makes this a memorable read.

— RT Book Reviews

Hot and spicy, this romance was written for all of those readers who like both the good—and the very bad.

— Library Journal

In The Duality Principle, Rebecca Grace Allen introduces us to one of the sweetest reformed rakes ever.

— Heroes and Heartbreakers

The Duality Principle is an exceptional debut with a scorching combination of smart meets sexy.

— Tara Sue Me, NY Times bestselling author of The Submissive Series

A gorgeous, sexy debut from Allen…hits all the right super emotional notes.

— Charlotte Stein

Scorching hot sexual tension that sizzles through the pages…Recommended for those who love stories featuring sexy as sin, reformed bad boys who just can’t help but be bad with the right woman!

— Maldivian Book Reviewer

There’s sexual chemistry, that’s for sure (and fantastic). But there’s also an emotional chemistry that just really made me fall completely in love with these two and their story.

— Amazon review

4.5 Fabulous Stars!!!!!!!!!

— Mia's Point of View

A hot, steamy and intoxicating read!

— Goodreads review

Gabriella and Connor are hard to resist–and an absolutely perfect blend of naughty and nice…The Duality Principle is a brilliant play of romance.

— Amazon review

I love how sweet and considerate Connor is when all Gabby wants is to get down and dirty. A very fun read!

— Lily Maxton

A really fun read with some drama to keep things interesting and incredibly sexy sexy-times.

— We So Nerdy

Other Books in the The Portland Rebels Series

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