I’m Only Wicked with You by Julie Anne Long

The bestselling author Julie Anne Long continues her Palace of Rogues series with a brand-new romance about an ambitious American and a headstrong British heiress.

He’s the battle-hardened son of a bastard, raised in the wilds of New York. She’s the sheltered, blue-blooded darling of the London broadsheets, destined to marry a duke. Their worlds could only collide in a boardinghouse by the London docks…and when they do, the sparks would ignite all of England.
Nothing can stop Hugh Cassidy’s drive to build an American empire…unless it’s his new nemesis, the arrogant, beautiful, too-clever-by-half Lady Lillias Vaughn. The fascination is mutual. The temptation is merciless. And the inevitable indiscretion? Soul-searing—and the ruination of them both. Hugh’s proposal salvages Lillias’s honor but kills their dreams for their futures…until they arrive at a plan that could honorably set them free.
But unraveling their entanglement inadvertently uncovers enthralling truths: about Lillias’s wounded, tender heart and fierce spirit. About Hugh’s stunning gentleness, depth, and courage. Soon Hugh knows that as surely as he’d fight a thousand battles to win her…the best way to love Lillias means breaking his own heart.