Something Fierce by Jenika Snow

When Tristan got a new roommate in the form of a six-foot-three tattooed and pierced beast of a man, she wasn’t prepared for the instant lust that claimed her. She should have made sure this stayed strictly platonic in nature, but it seemed Kash might have other plans in mind.
The attraction was magnetic and powerful. It was undeniable, no matter how hard they fought it.
When she stumbled upon an underground cage fight, the last person she expected to see was Kash, bloody and bruised and destroying his opponent. She should have run the other way, but instead she found herself aroused and wanting him even more.
Kash was a fighter and a damn good one at that. He’s stayed away from relationships and focused on his craft.
And it’s worked out well for him … until now.
He didn’t mean to get involved with his new roommate, but the curvy little brunette had every possessive instinct in him rising. From the moment he saw her, he was obsessed.
But those well-thought-out intentions are a thing of the past.
Now that he has Tristan, he’s not letting her go.