This might have made a good novella. I just read a blurb that said Anderson will be best remembered for this book. I hope not. Some of his work is very good, some is great. This isn't.
I guess it qualifies as "hard science", because no laws of physics are violated (though I think nobody actually believes in an eternally, repeatedly, expanding and contracting universe any more). But the laws of probability are given a pretty hard shakeup.
And the whole premise of why their ship is forced to voyage onward forever after an accident makes it impossible to stop at their target star is just not believable.
In a group read with Sci Fi Aficionados, one participant complained that the characters are poorly developed. She was being generous. Our "heroes" travel to the end of the universe, and in all that time, only one character gets developed at all (Reymont) and he is notoriously close about his character.
I just kept hoping for it to end.