It's been a bit of a theme in my recent reads too. I reviewed "The Body Institute" back in September, and then read The Hybrid Chronicles and the Starters/Enders series ... all completely different in storyline, yet they all had a similar feel, with more than one person in one body (and their covers all have a similar light blue look too!)
I experienced this as an audiobook. Not the best narrator, she was a little dry ... but I enjoyed the story. In addition to the "mind swap" similarities, I've read several books where the post-apocalyptic situation was similar (although in "The Girl Who Owned a City" "Kahayatle" "Gone" and "Night of the Purple Moon" it was all just kids who survived. No adults. Here, the "grandparents" were still able to keep the world running more smoothly than in other apocalyptic reads.
There was one little moment that caused me to laugh out loud though ... one of the older gentlemen was talking and says "remember when we could travel? Now Mexico built that wall to keep us all out!" I just thought it was pretty funny considering the current political situation!
I really enjoyed "The Hybrid Chronicles" ... and I loved their covers! The consistency throughout the three books, the duality represented visually, the Me, We, Us emphasized in font and title. And such a unique idea! Everyone is born with two souls within them. For the first few years of life, both "children" are part of the family. As the child grows, it's expected that one soul will be dominant, and the other, recessive soul, will fade away. Can you even imagine? Even sharing one body, as a parent, having a child you knew you were going lose? It's just the way it is. There is a small, private mourning, then it's not really talked about and life goes on. It's NOT normal if one of the souls refuses to fade. Here, with Addy and Eva, Addy is the dominant soul and Eva is almost gone. No one but Addy knows she is actually still around. Eva is only a voice in Addy's mind, a presence. She can't take control of the physical body or speak ... until someone guesses that Eva is still there and works with the girls to help her regain those abilities. There are other "hybrids" out there but they are viewed with suspicion and taken for "treatment" ...
I listened to the first two as an audio download from my local library. Great narrator. Unfortunately book three wasn't available at my library in anything but a physical printed book. The thought of having to go to the library, pick up an actual book, lift the heavy thing to read it, turn pages, lug it with me ... what can I say? I'm a complete digi-convert! I actually paid $10 to buy the final book (couldn't quite justify the extra cost of audio, although I did miss the narration). I'd recommend this series and think back on it very fondly!
Parts of it reminded me a bit of The Tripartite Soul, which I also read last year. In that one, three different people have their own separate bodies (and one of them is a dragonish creature, not a human) but their consciousness is linked. As Addy/Eva could leave to "leave" to give each other a bit of privacy, so could the characters in this story build walls to attempt to shut each other out a bit.