A long Hindi story can be engaging if it has a strong theme. For instance, stories that revolve around the themes of love, loyalty, or the battle between good and evil. Take the story of 'Savitri and Satyavan'. The theme of love and Savitri's determination to bring her husband back from the dead makes the story very engaging. Also, the use of dialogue that is both natural and reflects the characters' personalities helps in making the story interesting.
Character development is key. In a long Hindi story, if the characters are well - developed, like in 'Panchatantra' where each animal character has distinct traits, it makes the story engaging. For example, the sly fox or the brave lion. Another element is the plot twists. A good long story like 'The Monkey and the Crocodile' has plot twists where the monkey outsmarts the crocodile in an unexpected way.