The ﬁrst entry in Sean Williams' Astropolis trilogy, Saturn Returns had enough "hard-ish" sf staples to catch my interest (although I must admit that in reality, I bought the trilogy purely because of the title - it was bought during a particularly irresponsible book splurge with my girlfriend in the local Dragon's Lair): It deals with the remnants of a transhuman galactic civilization in which faster-than-light travel is explicitly not possible. Humans have mastered extreme longevity treatments and a variety of technology to alter perception of time - in fact, these technologies are the primary "SF gadget" explored in this setting. From the various methods of dealing with interstellar life in a setting where FTL travel is impossible, multiple different humanities have emerged.
The story itself is basically a murder mystery, albeit one with considerably higher stakes than most - in fact, it's probably better described as a "genocide mystery": An ancient, galaxy-spanning human intelligence was entirely wiped out, and with its collapse came the collapse of civilization itself. The POV character has been dead for 150.000 years when the story starts, and has been restored (although gender-ﬂipped) from a damaged record found by a religious hive mind looking for God at the edge of the galaxy.
Unfortunately, while the setting had lots of cool ideas in it, a lot of the background was frankly nonsensical. The aforementioned galaxy-spanning intelligence apparently has less aptitude designing reliable communication networks than modern-day Internet engineers, because a transmitter disruption is enough to kill their entire civilization.
The 150.000 year gap between the events of the story and the historical events remembered by our reconstructed POV character Imre Bergamasc seems more like a small delay than like the almost incomprehensible stretch of time 150 millennia actually is. In Saturn Returns, Imre returns to familiar star systems to meet old associates of his and to ﬁnd a culture easily recognized by him. In contrast, 150.000 years before I wrote this, the Ice Age had not yet begun. Cro-Magnon man hadn't made it out of Africa. Metalworking was unknown. Nobody had thought of agriculture. Animals hadn't been domesticated.
The consequences of the lightspeed limit are sometimes taken very seriously, sometimes apparently completely forgotten (or ignored). At some points, star systems appear to have real-time communication between one another, at other times this is explicitly declared impossible. The time perception alteration tech also works rather inconsistently (and bizarrely, people who are Overclocking sometimes seem to be able to move at stupendous speeds, despite the fact that this is at other times explained as strictly a brain modification). There are many references to "absolute time" and the "absolute calendar", but it's a well-known scientific fact that absolute time cannot exist in our universe.
All in all, the setting left me with an impression that this was basically a "poor man's Alastair Reynolds". Many of the same tropes are there, but the implementation is nowhere near as consistent and well-thought-through. It's a honest attempt at "hard" science ﬁction, but unfortunately has so many inconsistencies and science botches that it falls rather ﬂat.
A few parts were cool (the time-perception alteration was a neat idea), a few parts were meh (the interaction between the lead character and his former mercenary colleagues were mostly dull exposition dumps and exchanges of clichés), and a few parts seemed completely superfluous (having the main character be reconstructed as a woman after his death for no apparent reason and with no real significance apart from a bizarre scene dealing with a man's mind in a woman's body while masturbating).
I'm probably still going to read the rest of the trilogy, but the Christmas harvest of good SF books bumped them down my reading list.