Without knowing why, our narrator describes his life as a man who stays the same for millennia, even as others, one-by-one, are disinterred, slowly grow younger and younger.

The story is soft-spoken but moving, and for me, it was a good complement to T.H. White’s backward-time-traveler, Merlyn.

The title suggests that Professor Amos Shute’s intrepid travelers are going back in time to four planets that are identical in every way to our own, but then again, perhaps those four planets were merely at earlier times to begin with. We won’t say one way or another, but we are glad that the Spanish Flu pandemic, World War I, World War II, and World War III were all averted on some Earth.

In early 1960, Perry Mason author Earl (not Erle) Stanley Gardner and his wife host John W. Campbell, Robert Heinlein, Clifford Simak, Edward Teller, Ronald Reagan, Douglas MacArthur and Jackie Kennedy to discuss a shared dream in which a time-traveling alien requires them to pick one person to eliminate from history as a prerequisite to a final revision of mankind’s history.

Victor is one of the many protectors of the timeline from rogue rewinders. In his case, his five-year mission is to protect a small dark-haired boy in 1894 Austria.

A twist on how meeting yourself for coffee interacts with how time travel works in your universe.

In one instantiation of her life, Ursula Todd dies just moments after her birth in 1910. Fortunately (for the sake of the novel), time seems to be cyclic, so she and the rest of the world get many chances at life. At times, she partially recalls her other lives, resulting in many consequences to history and her personal development.

After fifteen years of estrangement, bookish Zelda Jones reunites with her best friend from high school, Cassie . At the start of their new relationship, it’s not apparent that their interactions are going anywhere, but as the other main characters weave their way into the plot, Zelda learns about time travel on a single, static timeline, and the pieces lock nicely into place.

Oh, and Dave’s grandfather had a plot to go back and kill Hitler, but that’s not really relevant to Zelda (and Cassie and Walter and John and Charlie).