This is book 1 of the "Bowl of Heaven" series.

This note contains spoilers for the book.

Start of a new series, with a new huge object—the shipstar, a star with a huge cup that many races live on, propelling itself through space by a jet excited out of the star and passing through the Knothole in the center of the cup. The cup rotates, and the edges are the populated area.

The humans get there on a ramscoop ship, using cold sleep. They're actually bound for Glory, which has been robotically explored and looks worth colonizing. There is a colony on a planet around Alpha Centauri that's mentioned. These colonizing trips are long, slow, and uncertain, and are not portrayed as a solution to any particular problem. Glory may be emitting strange gravity waves, but the humans think it's at least as likely to be something behind it, far away. The Astronomer birds on the Shipstar seem to think it's Glory, and they probably know more.

The humans accidentally catch up with the Shipstar from behind; it hasn't been detected from Earth as of when they left. (We see the leaving, then we jump forward to when the on-watch crew starts waking people up to deal with the Shipstar sighting. Also, conveniently for the plot, the ramscoop isn't producing quite the projected thrust, so they also have a time/food problem (which waking people will exacerbate).

Ramscoops are rather out of fashion, since some later research suggested they'd produce 9x more drag than thrust, so they're kind of an anachronism here. Niven used them heavily back before we knew better.

So, the newly waked crew gets split into three groups, two on the Cup and one in the ship (which we hardly hear from). We also have a point of view among the Astronomer birds. The population of the Bowl is old, adapted to low gravity and to eternal sunlight. It consists of the original occupants, apparently (well, their species, descendants) with their supporting serf races, plus the "adopted", aliens they met and took some of and trained or modified to be useful.

I'm finding some of the wandering around surviving a bit boring right now; dunno if there's going to be enough payoff from the things we're learning, doesn't really feel like it. But we did just get a signal to one group from either the birds or the other group, encoded in visual images in huge lights or mirrors interplanetary distances away in a different part of the bowl. This is not, at least, a small novel.

We do end without resolving much; the humans are still split into three groups (two parties on the Bowl and one still on the ship). One of the parties has made a working partnership with one of the Adopted species, and has engaged in warfare against the Birds. And we're given hints that the Bowl has at least visited Earth before, and a slight suggestion that it originated on Earth. There's also mention of a Great Secret (perhaps that the Birds now in charge aren't the original builders?)