Mark is annoyingly perfect, but this still worked pretty well up until the end, when it went completely hearts-and-flowers in a completely unbelievable way.
I am also annoyed that even with a prostitute heroine and a virgin hero, the hero ends up being more assertive and sexually confident than the heroine. Oh, romance novels.
Milan always has a point around three-quarters of the way through where the heroine finally explodes/asserts herself and the man goes away and then reflects and comes to the realization that she's right and he hasn't respected her opinions/independence enough. And this private reflection is clearly part of Milan's thematic point, but narratively and emotionally it's unsatisfying -- the major emotional rapprochement between the two effectively takes place with only one present.
Heroine's best friend could have used a LOT more fleshing out. Despite lip service to the power of female friendship, this doesn't pass the Bechdel test.