An Arranged Marriage by Jo Beverley

Ruined through her vile brother’s schemes, Eleanor Chivenham is offered rescue by marriage to a rake with an infamous French mistress. Eleanor accepts, determined to treat the arranged marriage with cool dignity.
Then she meets Nicholas Delaney. Not only does he stir her senses, but the trouble and pain beneath his smooth exterior reaches her heart.
Nicholas is indeed troubled. While serving his country by seducing secrets out of a French spy, he is persuaded to marry Eleanor to protect his family’s honor. But such chivalry runs counter to his carefully wrought rogue image, and extends the life-threatening plots shadowing him to Eleanor.

To assist, Nicholas re-assembles the Company of Rogues, a schoolboy group he started years before. But not even they can dampen Eleanor’s fighting wit that is quickly unmasking their enemy and testing Nicholas’ formidable will.