It was! The whole book plays a lot with various types of consciousness. Although that was a bit of a spoiler, so out of respect I'll give a somewhat obfuscated link and just say if you're reading something by Alastair Reynolds right now you should consider that before following the link:
(Reynolds' got enough books in his bibliography I don't feel like I'm spoiling anything by mentioning his name - I suspect I could come up with any random plot point and he's probably written it in somewhere)
Ah, I thought this was going to be Karl Schrœder's Permanence, in which (unless I'm confusing it with a different book) a background point is that consciousness is only really useful in some niches, and most spacefaring species eventually lose it.
John Varley had a short story with that idea, too. A spacefaring race that is only conscious when needed. Good sarcastic lecture about how consciousness is overrated by those who have it.
It was not, but that was also an absolutely fantastic book. I don't remember the sequel, Echopraxia, being as good, although there's a couple plot points from it that I do remember as weird ideas.
https://openlibrary.org/books/OL26809698M
(Reynolds' got enough books in his bibliography I don't feel like I'm spoiling anything by mentioning his name - I suspect I could come up with any random plot point and he's probably written it in somewhere)