If I were reviewing only the first book, it would have probably been five stars. Liu Cixin was off to a galloping start, not unlike John Steinbeck's Grapes of Wrath. Alas, just like Grapes of Wrath, Liu is unable to keep up with himself and the trilogy drifts toward more mediocre the further one gets. The opening chapters are particularly gripping and even surprising, given that Liu is a resident inside the People's Republic of China.
To his credit, Liu does a mostly good job trying to make more esoteric theoretical physics accessible to a wider audience, though one would do well to have some scientific understanding to grasp all that Liu offers. To American or European readers, Liu may come off as a little old-fashioned (or perhaps even a dinosaur!) in his understanding and description of romantic relationships.
However, he evinces little critical thinking skills and seems to accept many propositions at their face value. An important role for science fiction authors has been to be the conscience of science itself, as scientists very often consider the "How can I?" and not as much "Should I?" questions. It's notable that the first proposed "rules for robots" were proposed by an author and not a scientist. So while Liu's understanding and description of theoretical physics is admirable, one would hope for a bit more meaning critically considered.
Liu does touch on moral issues, but it seems in a more cursory, deterministic way. He touches on politics as well, but seems to want his cake and eat it too, sort of extolling the potential benefits of any given arrangement despite the contradictions with the other systems he also extols. Heavy on the science, light on other subjects.
All in all, it is an entertaining read. If you don't have much background in science, your eyes will probably glaze over in parts but the basic story will still be understandable. If you do, you may follow some of the given propositions with interest, or as in my case, with a healthy dose of skepticism ("that's why this is theoretical physics and not the real world, it's absurd and unworkable!"). It's worth following to the end, though it does become a bit tiresome by the time he finally finishes beating it to death. Below is a more detailed discussion that requires some spoilers.
<Spoiler alert> A prime example of Liu's uncritical thought is the dark forest theory Liu develops. It uncritically follows Malthusian thought, even though Malthus has been nothing but disproved since he first came up with that theory. Intelligent life like humans don't fall into the Malthusian trap like other animals because human genius comes up with ways to make required resources more rather than less abundant despite their consumption. It was such backward thinking in China's one-child policy that has led to the underpopulation crisis the PRC is now experiencing. While it is ultimately true that there are finite matter and energy in the cosmos and intelligent life forms may think of themselves competing in an ultimate sense for them, in the nearer term, as has been ably proven through millennia, cooperation and exchange vastly outpace conquest and destruction.
The use of dimensional weapons or weapons attacking the speed of light itself are particularly foolish given Liu's own premise, as they destroy these finite resources or at least make them inaccessible to the life forms competing for them. It would be a far more reasonable premise to assume the end of all things (the last of the stars burning themselves out) would pose a more immediate problem for intelligent life than their cohabitation with one another. Especially as, at least in the case of humankind, we see population shrinking not growing with high levels of education, culture, prosperity, etc. It would be a reasonable assumption that many other intelligent life forms might mimic this pattern, though each species' own biology could play a role as well.
Liu's proposition that life could even evolve or sustain itself in the Trisolaran system is really a bridge too far as well--I know it's science fiction and one can suspend some disbelief, but given the difficulty and unlikelihood of life in any system, even with favorable conditions, it really stretched things to think that such a civilization could be spawned from one-celled life forms and advance to the levels indicated despite the obvious destruction of organisms and habitat alike.
There are unfortunately many other lesser examples of Liu's lack of critical thinking. He seems to be convinced that humans quickly form a consensus about important questions and that this consensus is then carried out. Given that over 70% of polled Americans indicated they did not want a rematch between Trump and Biden, but they each won their respective primaries nonetheless, it is far from clear that consensus (if ever achieved) in any way connects to outcomes. Ditto for Rey Diaz finding a way for Socialism to "work," without any elaboration on how exactly that was accomplished. I would refer Liu to Ludwig von Mises's Socialism An Economic and Sociological Analysis by Mises, Ludwig Von ( Author ) ON Jan-01-1981, Paperback for a mathematical destruction of this idea, starting with the inability to conduct economic planning. Or one could refer also to Karl Marx's own admission of this fact in his theory of labor value as outlined in Das Kapital.