Nightfall's length at least comes close to squeezing into the novella or novelette category. In any case, I put it as his best short work, not to be confused with the later novelization published with Robert Silverberg. Blish, James Cities in Flight. Epic in scope, this tetralogy ends with the end of the universe and if, like many series, it isn't wrapped up in the most coherent or elegant way, it's still worth a read. Brin, David The Uplift Novels.
Humans stand out as foundlings who apparently achieved sentience on their own.
A fascinating concept well executed in novels of galactic intrigue. Other Brin novels such as Sundiver take place on the periphery of this universe. You'll see a few of them on this list since it's a sub-genre that I rather enjoy when it's well done. Card, Orson Scott Enders Game, Speaker for the Dead. A different view of an interplanetary war.