It’s in His Kiss By: Julia Quinn (Bridgerton Book 7)
This is the story of Hyacinth and her love life. This is now one of my favorites. Hyacinth in the last of the girls and 7th in line in the Bridgerton clan. Hyacinth finds herself falling for Gareth St. Claire. He is hated by his father and him and Hyacinth help him to discover his true identity.