Thomas M. Disch, an author, poet and critic who twisted the inherently twisted genre of science fiction in new, disturbing directions, including writing his last book in the voice of God, died on Friday in his Manhattan apartment. He was 68.

His friend Alice K. Turner said Mr. Disch shot himself. She and other friends told how his apartment had been devastated by a fire; then his partner of more than 30 years died; then his home in Barryville, N.Y., was flooded; and finally, he faced eviction after he returned to the apartment. He also suffered from diabetes and sciatica.

“He was simply ground down by the sequence of catastrophes,” his friend Norman Rush, the novelist, said Monday.

Mr. Disch’s work was voluminous and included many forms and genres. In addition to writing speculative fiction (his preferred term for science fiction), he wrote poetry from light to lyric to dramatic; realist fiction, children’s fiction and historical fiction; opera librettos and plays; criticism of theater, films and art; and even a video game.