This is another Asimov reissue I hadn't read since my initial seventh grade Asimov binge. It's a lovely new edition, but frankly I'm beginning to think I was wise in sticking to Robot books and Foundation books in my rereads. I'm not sure that the message of this one was supposed to be "celibacy and time travel: they will both make you batshit," but then again I'm not sure it wasn't, either.
So when you read a classic-but-not-much-read-these-days SF novel like this, it is of course with a huge grain of salt labeled "context of its time." But Asimov has done better than this in this period of his work--most of his famous SF novels were all written very close together, so while there's some "he changed with the times" potential with his later period stuff, a lot of it is packed in together, hard to think of it as a change in attitudes when it's essentially the same guy doing better and worse with different books. Compared to The Currents of Space, the cultures in this book were somewhat more fleshed out: the eras in the time stream, unlike the planets in the galaxy, would have multiple attributes and tendencies. So that part was, if not objectively better, certainly more to my taste.
On the other hand...um. There is some major, major disability fail in this book--apparently they will not have invented wheelchairs by the 222nd century AD? Or something. But not something awesome. Also there was only one woman in this book, and her name was Noÿs. So...the sole female character is either "noise" or "no is," as in Nonexistent, and in the context of the book the latter was entirely possible as meaningful. Noÿs ended up with a fairly meaningful role at the end that indicated she'd been underestimated all along, so that was good, but it meant that through the entire book, women were either simply absent or patronized to within an inch of their lives. Even a woman from a supposedly (nearly unique) matriarchal culture. Whee.
The review copy on the back of this book talks about who it has influenced, and I think it did contribute to the discourse of time travel novels, but I think it's one of the ones that's better skipped; you'll end up thinking better of both time travel novels and Isaac Asimov if you read a Robot book and a Kage Baker book instead.