After being disappointed by Book2, Book 3 was a return to the form of Book 1. Morning Star rattled along at a good pace with more than just fighting/plot exposition. All the plot strands get brought together and tied off nicely. 
 I was also impressed that I enjoyed the book despite the fact that I had forgotten a lot of what had happened previously (there was a 5-month gap between books 2 and 3). To get the most from this series, I'd recommend reading the books as close together as possible. The cast is large, there are many settings, the scope is epic. Unless you have an excellent memory it's tricky to keep track of everything that's gone before. 
 The world-building, the sheer work that went into putting together the detail of Pierce Brown's solar system-wide society, is breathtaking. On the other hand, his characters tend to either be great or flat. This two-dimensionality even extends at times to the main character, Darrow. In fact, the best character in the whole series is Sevro who, in book 3, is elevated to scenery-chewing greatness. If this series is ever adapted for film or television, Sevro is the role actors should scramble for. 
 I've posted a spoiler-free review of the whole Red Rising Trilogy on my book blog.