Things I Liked: 
 The unspoken parallels between humanity and the Trisolarans. In the first book, we were treated to a human-coded history of Trisolaris, and the never-ending struggle to escape an inevitable fate. Here, humanity faces their own unsolvable problem. 
 Surprisingly, Zhang Beihai. I think he was probably my favorite character. How much this was affected by Cixin Liu's creative murder scenes, I couldn't say. 
 The social change Luo Ji and Da Shi experienced 200 years into the future. Other books have explored the concept more thoroughly (for example The Forever War) but it was nice to see a callback. And, of course, the complacency and casual arrogance of the future. 
 The entire space scene's execution (minus human stupidity). (view spoiler)[I'll admit, though, the 'mind meld' thing was odd. Still deciding if they were actually hearing each other or if the chains of suspicion were that obvious. (hide spoiler)] 
 Things I Didn't Like: 
 Luo Ji's entire romance arc. From the imaginary lover to her fulfillment as an actual existing person, she perplexed me. Initially I thought that her role might be as Keiko's turned out, but no. She's just there to act as a living-doll muse, and I don't know how to respond to that. 
 There were a few plot holes. Well patched, but still there. Do people know or not know what Zhang Beihai did? His conversations would seem to indicate both are true. Also, what was up with the Imprinted? Did they exist or not? 
 The stupidity of setting a space fleet up like old-time cavalry. Really? Are humans that dumb? 
 That ending. I understand that it was meant to be a kind of mutually assured destruction--the weaker party might not be able to win, but they can eliminate the victory prize--but it seemed weak. It certainly doesn't eliminate the "chains of suspicion" from play. I imagine the third book will have something to say about that, because the end of this book felt less like resolution and more like detente. 
 Conclusion: 
 Having enjoyed The Three-Body Problem, I was looking forward to seeing how Cixin Liu handled humanity's impending destruction. Ultimately, I enjoyed it, but it's not without some serious flaws. 
 The ending was weak, for mid-trilogy fare. Now we'll need to rebuild all of the narrative tension for the third book (though I could be wrong).