Initial reaction: That was a satisfying end to a good series overall. A few points for me had the narrative dragging but I enjoyed the journey overall.
I'll admit I'm a little sad to be finishing this series with "Echoes of Us" for two reasons: 1. It took me a long time to pick up this final novel and 2. This is pretty much the end of the journey for Eva and Addie. I've spent three books following these characters and found myself invested in their fight for representation and non-erasure of hybrid souls. This book has Addie and Eva delving into an alternate identity once again by going undercover at a facility with hybrid children like themselves to expose the horrible treatment of the souls there, but it comes with a high cost.
It may be a better thing for those who are reading the series to read these books back to back because I did struggle a little in the transition between this book and the last for remembering certain details and characters (though the book does a fair job of highlighting some of the major events from the previous books that Addie and Eva were involved within). Once I reacquainted myself with events, I was okay for the most part. I wasn't expecting some major character deaths from the get go - when the action hits home, it definitely hits home. I definitely felt for Eva in the midst of the novel for the separation anxiety and loss she feels on multiple levels. The novel on the whole ties up the major conflicts in a way that - to me - was one of the strongest ends to a YA series that I've read in recent times. However, I feel like there could've been more time spent with respect to the character development and some of the plot points that really didn't have a lot of answers with them (i.e. the existence of hybrid souls vs. the general public and how that related to the international conflict). I can't complain on the whole though, this series collectively had me glued to see what would happen next in Eva and Addie's overarching journeys.
I'm going to miss following these two - wonderful audiobook narration by Kim Mai Guest and a unique YA dystopian trilogy that left me with great impressions. The only thing I wish in finishing the novel (and series) is that it could've delved a bit deeper.
Overall score: 3.5/5 stars.