This book raises the question: How to write a genuinely new alien invasion story? Ever since H.G. Wells' "The War of the Worlds," the genre has been littered with variations on the same theme, both in literature and film. It goes something like this:
Initially inscrutable alien spaceships appear in our skies. Mankind looks up in awe and fright. Then Bad Things start happening. The humans wise up; the aliens are here to Take Over the World, although the way in which they attempt to do so seems curiously anthropomorphic. Life as we know it comes to a crashing end. Meanwhile, a savvy network of resistance fighters gradually realizes the omniscient-seeming aliens have a convenient weak spot. The rest of the story dutifully chronicles the humans' effort to eradicate the alien presence.
Thus far, Silverberg hasn't deviated from this formula one bit. I'm not saying it's a bad novel, or that surprises aren't in store. But I expected something uniquely Silverbergian, a sense of the surreal that's (so far at least) disappointingly absent.
Interestingly, there's a cop-out authors use when they release a Wellsian invasion novel: They simply proclaim that their novel is a loving homage to Wells. True, it's tempting to crank out a page-turning variation on the "War of the Worlds" theme (the temptation to employ cool literary special effects alone is enticing enough for many authors), but the homage bit is played. I'm not sure I buy it anymore. How many tributes does Wells need? Is it conceivable that SF publishers are inclined to publish formulaic Us vs. Them novels because they tend to sell?
The last really good alien invasion novel I read -- John Shirley's "Demons" -- wasn't about ETs at all; the villains were supernatural. But they were genuinely weird in a way that Silverberg's invaders are not.
Another extremely good alien novel (not quite an "invasion" story, but related) is Whitley Strieber's "Majestic," a truly creepy fictionalized reconstruction of the Roswell UFO crash (written, incidentally, long before "Roswell" became a paranormal buzzword). Check your local used-book store.