I can understand why some Heyer fans didn't enjoy this one as much as some of her other work, but Lady of Quality worked really well for me. In this case, I liked that the relationship was cemented part way through the novel, thus allowing for some exploration of "post courtship". 
 A different secondary relationship, between the younger characters (a staple part of Heyer's novels), was explored here as well. 
 Personally, I found it refreshing!