In Episode 1, Daphne Bridgerton and Simon Basset, Duke of Hastings, cross paths by bumping into one another following an uncomfortable encounter between Daphne and her relentless and loathsome suitor Nigel Berbrooke. However, in The Duke and I, Simon spies on Daphne while she converses with Berbrooke and comes to her aid after she punches him. That altercation doesn't happen in the series until Episode 2.

The Duke of Hastings' experience overcoming his vocal stutter as a young child plays out similarly in both the books and the Netflix series, but in the books, it's still present well into his adulthood. It even complicates his relationship with Daphne as he does not want to stutter in front of her or pass it on to their eventual children. Finally, Simon ends up trusting Daphne enough for her to see him as he is, which was a major breakthrough for their relationship.

While Simon's shirtless scenes in the boxing ring are a highlight of the Shondaland series, they're absent from Quinn's books. Simon doesn't get close to many people in the books due to his stutter, but since that storyline is missing from the streaming series, the Bridgerton writers added the boxing plotline to fill its place. However, it's not entirely unlikely that the Duke of Hastings would enjoy spending some time in the ring considering the Regency era was the peak of boxing in England.

In the books, Anthony isn't as protective and overbearing as a brother to Daphne. In fact, Daphne and Simon actually tell him about their ruse, which he agrees to keep a secret as long as the two are never alone together. But when he catches them hooking up in the garden, he becomes furious and challenges Simon to a duel.

While the Netflix series follows Daphne as she begins her search for a lifelong partner, the book series finds her in her second year on the marriage market. The queen isn't as enamored by Daphne, and she certainly doesn't refer to her as the "diamond of the season." Though, a similar theme in both the series and the books is how Daphne has a hard time finding a suitor and enters a pseudo-relationship with Simon to better her chances.

Daphne and Simon's disagreement over having kids is still a major part of their relationship in The Duke and I. In the Netflix series, after she realizes that Simon pulling out during sex might prevent her from getting pregnant, Daphne gets on top of him and controversially ensures he won't withdraw from her — despite him asking her to wait.

Critics have discussed how that scene deals with consent, but in the book, it's an even murkier situation: Simon is drunk and asleep when Daphne forces him to finish inside of her. Readers interpreted the scene as flat-out rape, and Regé-Jean Page told Oprah Magazine that he "was very happy that we had a different scene in the TV show than in the book."

In the book series, Mr. Featherington does not exist, and he certainly isn't addicted to gambling. Instead, Mrs. Featherington is already a widow. Therefore, the story arc of her husband dying at the end of the season and leaving the family financially unstable isn't present in the books.

Judging by Mrs. Featherington's ill reaction toward whoever is the heir of her late husband's estate, it's not someone she's fond of. Because there's no premise for this in Quinn's books, the fate of their estate is a significant Season 1 cliffhanger.

The book series hardly follows Marina Thompson. And when she is mentioned in the fifth book, To Sir Phillip, With Love, she's already dead and merely the late wife of Phillip. That means her entire storyline — including her pregnancy and relationship with Colin — was strictly added for Netflix.

Lord Featherington isn't the only character created specifically for the Netflix series. Quinn doesn't mention Siena Rosso in the books, but Siena seems to draw inspiration from Maria Rosso, an opera performer who appears in the Anthony-centric The Viscount Who Loved Me book. Benedict Bridgerton is an artist in Quinn's books, but he doesn't attend any art parties and therefore never meets Sir Henry Glanville, a character created for the Shondaland series. In the books, Daphne never encounters a prince — Prince Friedrich only appears on screen.

Another Netflix-created character: Benedict's love interest and the town's go-to seamstress, Genevieve Delacroix. His only love interest on paper is Sophie Beckett, which leaves viewers wondering where his relationship with the beloved dressmaker will go in future seasons.

Finally, despite existing in real life and ruling England when the series takes place, Queen Charlotte didn't appear in the books. Instead, she was added into the Bridgerton universe by Van Dusen for the show. "What really struck me with the books from the beginning is that this was an opportunity to marry history and fantasy in a really exciting, interesting way," the showrunner mused to O magazine. "So in Queen Charlotte, that was the history. And then it was thinking of these fantastical scenes and situations to put her in that were really fun to write, too." Unlike many of the other non-white characters, it's historically likely that the queen was Black.

The Penelope-is-Lady-Whistledown reveal came as a shock to fans of the books, who remember that Quinn didn't reveal the gossip writer's identity until Romancing Mister Bridgerton, the fourth novel in the series. In turn, the queen never asks Eloise to conduct an investigation.