I have often hoped someone would write a good science fiction novel or series about the extreme future of humanity, in a universe where physics as-we-know-it is followed.  That is, where technology does much that is not forbidden but nothing that is forbidden.  In particular, I wanted to read a novel about a pan-galactic super-civilization where the speed of light is an inviolable limit.

This would not mean that interstellar travel is impossible:  time dilation would mean that a human could cross the galaxy in much less than a lifetime.  A simple relativistic calculation shows, in fact, that if one accelerated at even one gee, one could cross the observable universe in a single (subjective) human lifetime AND have the equivalent of comfortable artificial gravity the whole way.

Stein Sigur�sson pointed me to House of Suns, by Alastain Reynolds, which very nearly fits the bill.  Readers familiar with my series on waste heat an alien civilizations will find much familiar here, including Dyson swarms, infrared bright civilizations, galaxy-spanning super-civilizations, and more.  Indeed, Reynolds is an astrophysicist turned successful SF writer, and his evident familiarity with the possibilities and limitations of physics is used to good effect.  In the tradition of Asimov, Niven, Forward, and Clarke, he uses the possibilities of future physics and technology to drive the story and setting, instead of using technobabble as an excuse for violating physical law or a crutch for plotting convenience.  You can almost imagine Reynolds as scolding father to other authors:  “In this House you will respect the speed of light, young man!”

In House of Suns, we follow a pair of “shatterlings”, immortal clones of an ancient human, as they explore the future galaxy, filled with the descendants of humanity, and solve a mystery of increasing scope and importance.  In this universe, humans’ descendants have the galaxy almost to themselves, but light-travel time keeps various civilizations distinct and mostly independent.  The vastness of the galaxy keeps the scale epic, even as the action remains focused on a relatively small cast of characters.  Civilizations rise and fall between chapters as a the protagonists use a combination of extreme longevity, relativistic time dilation, and multiple forms of stasis, hibernation, and similar techniques to cross vast gulfs of space and time.

Reynolds keeps the readers’ attention by alternating POVs between the two main characters in the first person, and introducing each section with vignettes from a third perspective, whose relevance becomes ever clearer as the final reveals approach.  

Reynolds leans heavily on well-known SF tropes without dwelling on them (or even explaining them), which keeps the plot moving but might leave those without any SF background lost: “Priors” (the no-longer-present previous galaxy-spanning civilization), “whisking” (some sort of short-range transport technology, used often but never described), ringworlds made of impermeable materials (straight out of Niven), AI, and wormholes (used here in a GR- and causally-rigorous way) all play prominent roles.

The few liberties he takes with physics and plausibility are neither egregious nor completely impossible, and so forgivable (such as inertial damping (to use ST technobabble)).  My only major quibble with technical plausibility is that technology seems to have reached a peak over a several-hundreds-of-million-years span, with the same ships and tricks showing up a full galactic rotation later without becoming obsolete.  Despite this being a future where technology enables humans to cross the galaxy multiple times, the effectiveness of interrogation technology seems to have actually regressed since today, even as its showiness and expense have advanced.  Other minor issues come up too:  for instance, Reynolds underplays the importance of galactic shear and the peculiar motions of stars on rotational timescales.

Reynolds keeps the pacing brisk and the mysteries compelling enough to make this a page turner; it’s clear why he has several novels to his name at this point.  That said, like most paperback SF, House of Suns won’t be winning any awards for prose or philosophy; his metaphors are transparent, and the characters thin, sometimes little more than archetypes.   Though characters are well-differentiated, their voices are all very similar:  nearly everyone communicates in one of three modes: unfailingly polite, even obsequious formalities; familiar, exposition-driving conversation; or blunt defiance.  

The plotting is pleasingly twisty, but doesn’t appear to hold up under close inspection. Enormous leaps of logic and high levels of confidence follow from highly ambiguous “messages”: rings on the wrong hand of a corpse confirm a complex conspiracy theory; a hastily composed sketch of a few lines is (correctly) interpreted as a rather detailed last request.  Unless a closer reading reveals a reasoning that is not obvious to me, there are also some incredible coincidences driving the plot:  an emergency trip to an essentially random destination in the galaxy just happens to introduce the protagonists to an ancient being that is central to the mystery driving the action behind the scenes.  

But one rarely reads SF for its literary value, so all of this is really just quibbling. House of Suns is the first novel I’ve read that explores a mostly plausible extreme future of the Galaxy, and as such is one of the best SF reads I’ve had in a long time.  I strongly recommend it, and I’m looking forward to exploring more of Reynolds’ oeuvre.