Both the TV series and the book version depict how Agatha Danbury truly comes into her own after her much-older husband dies. Both versions also touch on how traumatized she is, due to what amounts to years of marital rape, and how negatively she views sex as a result.
In the book, the story focuses mostly on Agatha's quest to secure her family's future, with the only hint of romance coming through a brief courtship with Charlotte's brother, Prince Adolphus. The TV show, however, shows Agatha forming a bond with Lord Ledger, Violet's father, who is unhappily married to one of the racist ladies-in-waiting at court. She's ultimately able to take pleasure and control in bed, with a one-off affair with Lord Ledger that, decades later, Violet seemingly uncovers. The book skips this storyline entirely; in fact, Lord Ledger only appears once in passing.
