No mention of Peter Watts' Blindsight? That book changed all sorts of notions of first contact and consciousness for me. I'm still thinking about it to this day. Absolute must read for anyone concerned with such things
https://www.rifters.com/real/Blindsight.htm
Likewise, this is one I'll never get out of my head. Fair warning to would-be readers: anticipate the rest of your day becoming unproductive.
It was a Hugo nominee and actively reprinted under Tor Essentials label; probably doesn't qualify as a book "you may never have heard of"...but to be fair, anything by Andy Weir or Hugh Howey probably shouldn't have made the list either.
That's most of the ones being mentioned in this thread. I think maybe they are scifi books you haven't heard of...if you also don't normally read scifi.
The vampires appeared to have less of a gene pool and more of a gene cleanroom. Knife edge stuff there.
Which is weird, because they do.