Kind of interesting that this thread got revived the day after I finished the first Revelation Space novel

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I would say that novel kind of falls under a newish category -- Hard Space Opera. I think in several respects it falls just a bit short of what is required for true Hard Science Fiction... and it definitely is a Space Opera, but it plays much closer to real science than most Space Operas do. For example, while I really like David Brin's Uplift Universe, there is an awful lot in it that doesn't feel remotely plausible (the use of Psi for example); in contrast, while Revelation Space includes some really wild concepts... they don't feel nearly as implasuible. All in all, I enjoyed it quite a bit.
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Bill