Startide Rising was great--i remember it better than
Sundiver. There was a sequel to
Startide, too,
The Uplift War, all of them about the "Uplift Universe." (I think a total of six novels were projected--but i only read the first three.) Someone else (Frank Herbert? i disremember) wrote a couple of novels about sentient stars, too. Not high quality literature, though--more in the "action/adventure" genre.