Vernor Vinge has hit a home run twice in a row. A Deepness in the Sky
had all the fantastic alienness mixed with human drama and far future sci-fi awesomeness that made A Fire Upon the Deep
one of my favorite SF novels ever. I've become a lot pickier about my sci-fi, but A Deepness in the Sky
has held up even better than the first book in the twelve years since it was written.
At its heart is a conflict between two starfaring cultures: the Qeng Ho, a culture of interstellar traders who take the long view and regard planetary civilizations as customers, and the Emergents, a tyrannical empire powered by the secret of Focus, a virus that turns people into super-intelligent, docile slave-minds. The Qeng Ho and the Emergents arrive simultaneously at a strange star that flares into brilliance for a few decades and then goes dormant for centuries in a perfectly regular cycle.
On the single planet orbiting the OnOff star is a race of spider-like aliens who have evolved to live on this planet that is only inhabitable for a few decades out of every couple of centuries. When the Qeng Ho and the Emergents arrive, the Spiders are dormant, frozen in their deepnesses, but when the star flares to life, they are poised to enter a modern technological age in the next generation.
This three-way contest, with Qeng Ho and Emergents fighting a bitter war with each other full of treachery and dashed hopes, while the fate of the Spiders hangs in the balance, makes for a compelling story all the way through to the end. Vinge didn't drop the ball once, and he even made the Spiders relatable and interesting characters, so that the shift between human and Spider POV never annoyed me the way some books do when a more interesting character's story is left hanging to shift to a less interesting one. There is a whole raft of characters and you root (or hiss) for all of them. The book was epic and fully self-contained and one of the "harder" space operas out there, meaning it's mostly believable. Vinge does not rely much on hand-wavium to make his technology and plots work.
Just plain awesome. I give my highest recommendation for both this book and A Fire Upon the Deep