Nightshade by Michelle Rowen

Nightshade:
Jillian Conrad never believed in vampires. But she's just become a living, breathing weapon against them. Attacked by a desperate scientist, she is injected with a serum that was supposed to act as a deadly poison to vampires. And when the scientist is gunned down in front of her, his secrets die with him.

Declan Reyes is only half-vampire, but he hates them with all his heart. He knows that the poison in Jillian's veins could finally destroy the undead kingdom. The serum also makes her blood irresistible to all vampires--including Declan, whose bloodthirsty traits are driven into a frenzy be her.

Driven by duty to protect her and by instinct to crave her, Declan takes Jillian into his shadowy world of blood and battle. But he soon realizes his increasing need for her may be a different kind of hunger...

Michelle Rowen created an exceptional beginning to this series; a world where sometimes the good guys are bad, and the bad guys can be good. The characters were engaging and completely captivated me. There was never a dull moment in this book; passionate tension, intense action scenes and secrets fill every page. There are similarities in this book to a popular vampire movie, but with Michelle's unique story-telling I hardly noticed them.

Jill becomes thrown into a world she never believed existed, and all because she went for a coffee run. Returning to work, Jill is held hostage by a man with a syringe as he hopes to escape a terrifying man covered in scars. Things quickly take a turn for the worse when she is injected with a formula developed to kill vampires and the scarred man, Declan, kidnaps her and introduces her to his terrifying world. Jillian's only hope of survival depends on Declan and his scientist father, she resents having to depend on him until an attack leaves her caring for his wounds. Things change between them as Declan stops taking the serum developed to control his vampire cravings, for years he has taken it without question but once he stops, he is no longer a soulless assassin and he begins to have feelings. Jillian is captured by the vampire king and she learns truths from him that change everything she has been taught. No one is as she believed them to be and the only person she can truly rely on is Declan.