The Bobbsey Twins series follows the everyday adventures of two sets of fraternal twins: Bert and Nan, the older pair, and Flossie and Freddie, the younger pair. Early titles include The Bobbsey Twins (1904), The Bobbsey Twins in the Country (1904), The Bobbsey Twins at the Seashore (1904), and The Bobbsey Twins at School (1913).
Under the same pseudonym, the Syndicate also produced the Outdoor Girls series, beginning with The Outdoor Girls of Deepdale (1913), which featured a group of adventurous young women, and the Moving Picture Girls series (1914), centered on young actresses in the early film industry. Laura Lee Hope's books remain enduring examples of classic American juvenile literature.