"Stepsons of Terra" by Robert Silverberg

It’s the story of the Earth colony world Corwin, which is facing destruction from a rampaging horde from beyond the galaxy. (You gotta love those rampaging hordes. I do, anyway.) So the government of Corwin sends an ambassador to Earth to ask for help against the invaders. Unfortunately, Corwin is so far away from Earth that there hasn’t been any contact between them for 500 years. When Baird Ewing, the ambassador from Corwin, arrives on Earth, he doesn’t find what he’s expecting.

From there the book becomes a novel of political intrigue for a while, then takes a surprising turn and evolves into a time travel yarn. Silverberg damns the paradoxes and steams full speed ahead, winding up with an offbeat but entertaining space opera.

As you’d expect, this is a well-written novel with some nice plot twists. One of the things I liked about it is that it tells an exciting, fairly complicated story in about 50,000 words, and it stands alone pretty well, too, although there’s room for a sequel, which as far as I know Silverberg never wrote. No 150,000 word doorstop here, no trilogy that turns into an endless series of bigger and bigger books. Just a good solid SF yarn of the sort that, yes, I know it’s a cliché, they don’t write anymore. I thoroughly enjoyed this one, and I suspect many of you would, too. (Rough Edges)