This was a proper sci-fi in the sense that the author took an idea - in this case, "what if we could send information via microscopic wormholes" - and extrapolated from there. I have to admire the sheer number of ideas and thoughts in this book; when one avenue of wormhole use was described and its impacts on our protagonists and the world as a whole was established, an upgrade to the wormhole tech is introduced and the process repeats.

But some of the tangents were way too tangential, and the ending was way too 'out there' to be satisfactory. I guees most of the book felt 'believable' at some level - not in the sense that it could happen, but that people would (or at least could) react in the ways that they did. Compared to that, the ending felt way off. (It was similar to the ending of a different book of Clark's (I don't wanna spoil it here), but there it felt more appropriate.)

I guess if the book ended halfway through, it would get five stars. As it is, I can't decide between three and four, which is a bummer, because I really did like it.