This plot started and developed too standartly to be belived. How many books have you read already where the heroine is forced into marriage/sexual relations with the hero/scoundrel because of her family's gambling debts? In addition, we find out the the revenge bent scoundrel is actually a softie, who, though trying to get into his new wife's bed, is nevertherless trying to present himself to her as an unrepentant rogue regardless.
Of course, the heroine hates him at first, but then suddenly has a change of heart and climbs all over him. Plus, she comes to terms with the fact that he had married her to enter into Society, but gets all bent out of shape when she realizes that he is using her to get revenge on his father instead.
The love/lust scenes are good enough, I suppose and the secondary romance is fascinating. (Needed more info on it, though. Would have been much better book.) The final twist at the end is a bit redemptive, but Jamie's sudden change of heart is not explained. Why?
In short: close, but no sigar!