David Brin is one of my all-time favorite writers. His Uplift series is a great concept, and has served him to build a very fertile universe. However, I'd have to say that I like his more grounded SF even better. Earth is an excellent near-future novel, which is very tough to pull off. And then, after far too long away from SF, he published Existence in 2012. He'd been so long away, other than one short story I'd seen in 2009, that I didn't go get it right away, but received it recently as a gift.
And I would have to say that it's my favorite work of his yet. This is a very ambitious work, stretching possibility to the limit without breaking it. The reviews of the hardcover book say that one can read it as an Uplift preview, but the author makes it clear that this is not the case. He said that having Faster Than Light travel, like in Uplift, is like "playing tennis with the net lowered". This universe breaks no laws of physics, but instead speculates on what a cosmos that produces intelligent beings would look like if they were able to send something--a probe, a recording, anything--across the vast interstellar distances.
And what a rough place it would be. Brin's core thought is that any non-static object, like a self-replicating probe or an artificial intelligence in a small package, would undergo change over the millions of years it would be in transit. The spawning species would almost certainly be extinct by the time the artifacts made it to another civilization, with most never making it at all. If there were enough of them to actually encounter each other away from their home system, they might have evolved very different abilities, motives, and tactics from what their makers intended.
Existence is the story of what it might be like if earth received one of these evolved probes at some point in the not too distant future. Then, more, and more...could we survive the influence of devices so far removed from their makers?
Brin is an astute student of society, and has written much non-fiction on the topics of privacy, politics and sociology. His blog (on his website) makes for fascinating and inspiring reading. He deeply values diversity of ideas as a defining human strength and the key to survival--and I heartily agree with him.
So I give the book a rare four stars for execution, and a nearly impossible fifth star for all that went into it. More people should be reading and listening to David Brin, whether they agree with him or not.