The Redemption of Time by Baoshu
Imagine my surprise as I was walking in the bookstore next to Bryant Park one day and I see the headline "A Three-Body Problem Novel." And it was translated by Ken Liu...
The Redemption of Time is an authorized fan fiction (meaning Cixin Liu and his editor authorized it to be published and collect money on its sale) by an author, Baoshu. It addresses greater questions about the three body universe and has it's own plot line that ties various events together, following the lead of Yun Tianming and AA on the mini-universe.
Overall, I would rate the book lower than the original series but still interesting to read. It takes true creativity to be able to tie together plot lines as intricate as Cixin Liu's and I have a lot of respect for that. It got weird at times (i.e, with Sophon), but Baoshu makes up for it with sound game theory and creativity.