Times Without Number is a time travel story set in an alternate-history Earth. (Yes, the implications are pretty obvious. I won’t comment on them until after the spoiler barrier.) The book was originally three separate short stories. For this publishing, Brunner reworked the stories to create one narrative from them. Nevertheless, the book breaks easily into three different sections, each following a particular event in the life of “Don Miguel Navarro, Licencate in Ordinary of the Society of Time”. (The alternate-history is that the Spanish Armada successfully invaded England and Spain, instead of England, became the colonial empire of the West.)
The setting seems reasonably well-thought-out, if a bit chauvinistic. Women are second-class citizens, though that’s generally presented as a bad thing. There are slaves, which exist and are never commented on. Native Americans are all referred to as Mohawks, though some do express indignation at this. Time travel is the sole dominion of the Catholic Church; the creator of the original device didn’t think anyone else would behave properly with it. This book is probably not for anyone who would get offended at any of this. (It was written 1969; the original stories are from 1962. All well before political correctness came into vogue.)
Within the story are some reasoned explorations of various aspects of time travel. The Society has strict rules governing the use of the technology; naturally, the stories tend to hinge on the breaking of various of those rules. For me, this is the main reason to read the book. There isn’t too much here that hasn’t been explored in other time travel stories, but this one probably predates most others. Beyond that, the writing is decent, but not excellent, and it feels a bit dated.