Naked in Death (In Death, Book 1) by J. D. Robb

Eve Dallas is a New York police lieutenant hunting for a ruthless killer. In over ten years on the force, she's seen it all--and knows her survival depends on her instincts. And she's going against every warning telling her not to get involved with Roarke, an Irish billionaire--and a suspect in Eve's murder investigation. But passion and seduction have rules of their own, and it's up to Eve to take a chance in the arms of a man she knows nothing about--except the addictive hunger of needing his touch.