"Shikasta" uses stories and images from the Old Testament and is influenced by spiritual and mystical themes in Sufism. Lessing had become interested in this Islamic belief system in the mid-1960s. The book was a major shift of focus in Lessing's writing, from realism to science fiction. Many of her readers were unhappy with the change. Critics gave the book both good and bad reviews. Some were impressed by the way the book showed a wide view of humanity and the universe. One reviewer called it a brave "and disturbing work from one of the world's great living writers". Others reviewers disliked the novel because it was depressing and humanity had no free will. People's lives were controlled by galactic empires.