The books series is basically set up to make the TV series in an anthology format. Each book focuses on the romance of a new Bridgerton sibling with the others just playing small supporting roles, making cameo appearances, or no appearance at all.

It is a typical romance book series format which does not tend to gel with serialised TV shows where folks expect the same cast for the duration of the series. Which is why folks are shocked the leads from previous seasons are not returning for later seasons. Their stories are done.