It's a great book on the Fermi paradox, but with deep problems. Actually, the particular solution proposed in Existence doesn't seem to have made it onto the Wikipedia article or any listicles I could find, even now, over a decade after the book came out. That's probably because it's very quirky, but that doesn't make it not interesting. The book also includes many other short meditations on the Fermi paradox and the fundamental problems and contradictions threatening the core of human civilization. Some of the characters and action scenes are interesting. Some. I have a lot of issues with this book, but one major one far outshadows the rest: The autism nonsense manages to take up like 40% of the book, and it's completely clear that he's never talked to an autistic person before. Like, he's right: they aren't, as he's written them, human at all, they're weird aliens who sit around plotting weird terrorist attacks to punish... I don't think Brin actually understands what the high/low-functioning distinction is even supposed to be! And sure enough, his conclusion works that out: if I remember correctly, there end up being five species of humans sallying forth into the galaxy as one polity: humans, cyborgs, androids, high-functioning autistic people, and low-functioning autistic people. Oof. I'd say read this if you want to read every Brin book, or if you want to read every Fermi Paradox book. Otherwise, there are plenty of other options out there.