Three novellas.
The title story, "Threads of Time" by Gregory Benford, has a resourceful central character, a female lunar surveyor/archaeologist who begins by hacking her way out of a damaged vehicle to explore the alien defense system which has attacked her. The tension between the scientists and the New Sons, a religious cult with growing political clout whose basis is not really explained, is presumably intended to recall contemporary tension between science and religion in America. There is a parallel story tracking Bigfoot through the American forests, and the whole thing boils down to an extended and rather old-fashioned variation on a central idea of "2001: A Space Odyssey" (ancient alien artifact reveals contact with prehistoric hominids).
"The Marathon Photograph" by Clifford D. Simak is basically a meeting with a group of time travellers, and a chance for a bitter conversation about humanity's bleak future.
"Riding the Torch" by Norman Spinrad gave me the most pleasure. Humanity has had to abandon a war-ravaged Earth and head out into the stars in a flotilla of spacecraft seeking another planet, though developing their technology to such an advanced stage that they seem not to need one, except psychologically. Among the decadent high-tech socialites, Jofe D'Mahl, an artist in an operatic/cinematic genre of sensory stimulation, is challenged by one of the cult-like caste of planetary survey teams to confront the void, and then communicate the meaning (or futility) of human existence back to the rest of the population.
MB 6-x-2020 ( )