You're the Earl That I Want — Kelly Bowen

THE EARL DOTH PROTEST . . .
For businessman Heath Hextall, inheriting an earldom has been a damnable nuisance. The answer: find a well-bred, biddable woman to keep his life in order and observe the required social niceties. But it's always been clear that Lady Josephine Somerhall is not that woman. Once a shy slip of a girl, Joss is now brilliant, beautiful chaos in a ball gown.

. . . BUT THE LADY KNOWS BEST
In her heart, Joss has always loved Heath, the one person she's always been able to count on. That doesn't mean she wants to marry him though. Without a husband, Joss can do as she pleases -- and now, it pleases her to solve the mystery of an encoded file given to Heath by a dying man. It's put Heath in peril once, and Joss won't let that happen again. She'll do what she must to ensure the earl's safety. And to remind him that what she lacks in convention, she makes up for in passion.