They Shall Have Stars by James Blish
Might contain spoilers.
I’m aware that this was neither the first nor the best entry published in the series. The introduction by Adam Roberts to my SF Masterworks omnibus edition of Cities in Flight goes so far as to suggest skipping ahead then returning. However, I personally found it quite enjoyable, even hard to put down in its first third.
It’s certainly old fashioned in its writing style, in its language, in the views of its characters, and in its expectations from the reader (witness the many consecutive monologues). I don’t know that I came away with a clear impression of any of the characters, curiously enough. I can remember the names and roughly what they did, but I don’t believe I could describe them as people.
I wonder about the scientific explanations and at which points they begin to deviate from reality. It would be interesting to see how it holds up against our current understanding.
Next in series: A Life for the Stars by James Blish(#2 in Thoughts & Spoilers: Books: Cities in Flight (1955))