In the introduction to frankenstein how does mary shelley politely state that her husband percy is not suited to writing a goodghost story?

In her introduction to her novel Frenkenstein, Mary Shelley wrote en 1831 an account of the evening when Lord Byron proposed that a group consisting of Percy and Mary Shelley, John Willian Polidori, and Byron himself, should each write a ghost story, as a form of contest. Mary Shelley describes how each went about the task. In relation to her husband, she wrote: "Shelley, more apt to embody ideas and sentiments in the radiance of brilliant imagery, commenced one founded on the experiences of his early life." Percy Shelley, in fact, did not finish his story. Neither did Byron.