Time Travel discussion

I bothered to read this as it is the last story in The Time Traveler's Almanac., It's the longest at 52 pages or thereabouts. I believe it might only be an excerpt from the Novella of the same name, which goodreads lists as 131 pages (Palimpsest.) I thought it was good but felt incomplete and want to find the Novella and see if there is more to it. It's very Hard Science Fiction. Here is the plot summary from Wikipedia:

Pierce is a police officer with the Stasis, a special institution dedicated to the preservation of humanity by its agents who are able to travel through time. After every extinction event resulting in humanity's end, the Stasis reseeds Earth with a replacement group of humans time-jumped from an earlier era. However, the Opposition, an organisation that seems to struggle against the Stasis, has been created over time, and it seems that Pierce is somehow tied to it.