A pungent reminder of how deep my to-be-read stacks can get: Amazon tells me I purchased this item on June 21, 2000. Yes, nearly 20 years deep. (I kept putting other books ahead of it. Sorry, Connie.)
To Say Nothing of the Dog won the Hugo and Locus awards for Best (science fiction) novel, and was nominated for the Nebula. And this was in the pre-woke era of SF awards, so yeah, it's pretty good.
As an extra incentive, I was taken in by the dedication: which is a waving green flag that says "Read me, Paul":
Who, in Have Space Suit, Will Travel
first introduced me to Jerome K. Jerome's
Three Men in a Boat,
To Say Nothing of the Dog
And so I finally did. (And, like Connie, RAH's reference to Three Men in a Boat caused me to read that back in 2003. I was less taken with it than Connie was, but that's OK.)
Anyway: this book. In the near future, time-travel has been invented, but with a number of frustrating restrictions caused by the whimsical nature of the space-time continuum. Would-be travellers are prevented from transporting "significant" objects from the past back to their own time. And some "important" times in the past are impossible to reach. Otherwise, time travellers might assassinate Hitler, or prevent the assassinations of Lincoln or Archduke Franz Ferdinand.
Nevertheless, bringing back objects that were destroyed in the past are OK. Travellers can rescue them. And the lady bankrolling the time-travel project has demanded that an artifact called the "Bishop's Bird Stump" be rescued from Coventry Cathedral in 1940; it's been missing since the Nazi air raid. (What, exactly, is a "Bishop's Bird Stump"? Well, we find out eventually. Rest assured, it's hideous.)
Disclaimer: I may not have these rules exactly right. (And there are many more, it seems.) This book is Connie's second set in this universe, and the first one might have gone into more tutorial detail.
The narrator, Ned Henry, sets about this task. In the majority of pages, his detective work sends him back to 1888 England, where he takes up with that era's delightfully complex social mores. A whole passel of characters are introduced, a bunch of complications encountered, and confusion reigns as to whether what Ned does will end up ensuring a Nazi victory in WWII, or (slightly worse) destroy the entire space-time continuum.
It's a lot of fun, albeit way long (493 pages in my paperback edition).