The Viscount's Pleasure House (Irresistible Aristocrats Book 1). Irresistible Aristocrats, #1

Lady Chrissie Wellsby and her two country friends research dozens of rogues before selecting the notorious Viscount Hawkesbury, owner of London's most exclusive and expensive gentlemen's retreat, to educate them in the sensual arts. The ladies coerce Justin Tremayne into letting them visit his houses and to teaching them tricks to keep their men happy. Though Justin believes three naive ladies will observe his themed rooms, cover their eyes and ears, and run back to their country lives, he underestimates their determination to learn how to keep their men at home, and in their own beds.
But despite watching several of their friends perform raunchy acts, the ladies insist on participating in the last of Justin's infamous Sultan's galas. Justin concedes to Chrissie's demands only to gain information about his long-lost mother and sisters, but the world-weary viscount falls head over heels in love with his emotionally bruised pupil. He yearns for a wife, children, and an uncomplicated life, but can he convince Chrissie to take a chance and marry again? Because Justin never wants to leave her bed.