Unlike seasons 1-4 which are based on the first eight Poldark books, show runners admitted they decided to go off the books for season 5. Season 5 takes place between books seven and eight. Showrunners of shows based on books should stay with the books. The tone of this season is markedly different from the first four seasons. Likewise, new non-canonical characters are introduced. In an interview, it was said that went with this method because the other books dont focus as much on the main characters from the first four seasons. They should have followed Outlander, which kept with the books but changed certain aspects like characters to make it work. They could easily have kept the cast intact and adjusted the books to make the show consistent. Instead, they decided to go it alone when they didn't have the skill to be as good as the author.
Review of Episode #5.1
