There are several differences between the book and the radio broadcast of War of the Worlds. The novel was published in 1898, and the story is set in this time period. Moreover, the novel is written in the past tense. On the other hand, the radio program was broadcasted in 1938, and it was told in the present tense, in the form of news bulletins.
The radio version was probably more effective in creating fear of the unknown. Many people believed the show to be narrating a current event. Moreover, Welles's voice and sound effects contributed to creating a feeling of fear among the listeners.