Too Dangerous to Love (Project Viper #1) by Kristie Wolf:
 
He thinks he’s too dangerous to love.

Navy SEAL Chris Daviani lost his arm in action. Project VIPER gave him a bionic one. Now he’s stronger, deadlier, and much too dangerous to even think about the shy genius who turned him into the military’s first super soldier.

He should focus on keeping her alive while she uncovers a dangerous threat to VIPER’s existence, not on drawing out the sultry woman she's buried deep inside.

The flaw in his strategy? Underneath the science that’s made him a human weapon, he’s still a hot-blooded man.

She thinks the only thing desirable about her is her brain.

The men in Dr. Scarlett Kerrigan’s life have never valued more than her brilliant mind. The dark, intense SEAL is no exception. He needs her to save VIPER - and his career - but his scorching gaze makes her burn for the type of chemistry she didn’t learn in boarding school.

Problem is, her extensive education didn’t cover how to guard her heart against her alpha bodyguard who thinks his past has sentenced him to a life alone.

The solution? Even her brilliant mind can’t figure that out.