The "Duke Series" is a collection of romance novels written by Julia Quinn. Set in the early 19th century, the series follows the lives and romantic entanglements of the Bridgerton family, particularly focusing on the relationships between the siblings and their suitors. The series is known for its engaging characters, witty dialogue, and exploration of societal norms during the Regency era. The first book, "The Duke and I," introduces Daphne Bridgerton and her relationship with Simon Basset, the Duke of Hastings. The series has gained popularity for its blend of humor, drama, and romance, leading to adaptations, including a successful television series on Netflix.