I absolutely love her writing and this series has been such an interesting ride.
The one thing that deteriorated in my eyes from the first book, was human relationships. I can tell from her prose, that Octavia was a stoic and practical woman. Most of her characters are written this way. But not all people are like that. What I noticed and it tired me a little bit in the last two books, was that there is little passion or temper in any interaction. That might have impacted the pacing also.
Overall I think I won't forget those books for a long time, if ever. But as they stand strong in the group, there is one remarkable among them.