Until Midnight — Maya Banks

Her mother would absolutely die. Her father would send her away to a convent. And Sebastian and Quinn . . . she shuddered to think of her brothers' reaction were they to suspect what she was doing. Yet here she stood, poised to knock on the door of London's most renowned lover.

Lady Jenna's future may be promised to a man who leaves her cold, but she is determined to spend her present in the arms of Grayson Douglas, a rake whose prowess in bedroom activities is a legendary topic of London's most esteemed women. But she gets more than she bargained for as nights of passion turn into more and they both soon find themselves torn between duty and love.