In the same way I love android and robot stories because they point at what it is to be human, I love the Noumenon series for showing the different facets of humanity.
This book takes a wider approach and expands out from one convoy to show another's journey. We still get to follow convoy seven and their quest to understand the alien megastructure, but we also find out what happened to convoy twelve. Convoy twelve was briefly mentioned a few times in Noumenon as having "disappeared" during some kind of experiment gone wrong. Except: surprise! They are alive and we get to find out where and when they go. Lostetter does a great job of making readers care about the fate of several characters at once and even though a section would end, I was excited to see what happened to the other convoy (sections flip back and forth between convoy seven and twelve throughout the book). Both convoys have an AI, C (an earlier version of ICC) and ICC--which works as one of the many "glues" that connect the two narratives.
There were a lot of thematic touches that I adored. For one, the concept of survival and evolution to ensure survival were repeated and by the end of the book some of those points were incredibly emotional and revealing for me as a reader. Noumenon Infinity opens ideas and "what ifs" that are presented as possibilities and the characters must decide how to react to those evolutions. I was shocked and horrified, but also--what makes something "unhuman" or "a threat to our way of life" is dependent on context. The sacrifice of some traits/traditions may be necessary for the greater good, depending on the goals of that society.
Anyway, those are just deeper philosophical threads, for the most part this book concentrates on the journey of several characters and added new favorites to my list for the series. I'm desperate to find out what happens to Vanhi on convoy twelve for example, and what both convoys will do now because of events that happen by the end...I wish I could say but this is a book that shouldn't be spoiled!