I just finished reading The Affinities, by Robert Charles Wilson. Before I discuss my impressions, the usual disclaimer applies: De gustibus non est disputandum. I have only one criterion when I evaluate a work of science fiction -- did I enjoy reading it? So if your own tastes are similar to my own, you might find my comments interesting. Otherwise feel free to ignore everything I say.
My own interests run strongly toward "hard" science fiction, and I am a particular fan of "idea" stories -- these are stories where an amazing speculative idea is central, rather than character, or writing style. I also like clever endings. All of this is much easier to pull off in short fiction than in a novel. These kinds of stories are characteristic (in the golden age) of Clarke and Asimov, and more recently authors like Vernor Vinge and Greg Egan. Stephen Baxter is also someone whose novels I ought to enjoy, but I've never been able to make it through them. Why not? I haven't got the faintest idea. I warned you that my opinions are totally subjective -- sometimes I cannot even explain them myself. I do like Baxter's short fiction, though.
As I've aged, I've developed a greater appreciation for realistic characters and a more florid writing style. Perhaps this is incipient senility. It's the latter (wonderfully-drawn characters, not senility) that is Robert Charles Wilson's particular strength. When he's able to combine this with a Big Idea (as he did in Darwinia and Spin) the result is some of the best science fiction I've ever read.
The Affinities offers Wilson's usual excellent character development, but it falls short on the Big Idea. The novel takes place in a world in which psychometric testing has allowed humans to collect themselves into groups of similar temperament, with which they feel an automatic sense of trust and "belonging." A reasonable idea, but not one that really gave me a sense of wonder (to overuse that overused phrase). In fact, it doesn't seem all that implausible to be able to do something like that right now. Neal Stephenson had a more interesting take on this idea in The Diamond Age.
So on the whole, I certainly enjoyed The Affinities, but it doesn't rank with Wilson's best work. This also points out some important advice for new writers: if you never produce anything particularly outstanding, no one will ever be able to criticize something you've written as not measuring up to your best work. It has worked for me!