I don't know what to think about this book. Or more precisely, what to say. It wasn't bad, but I didn't love it. I didn't love the humans are bad for destroying earth message which has almost become a cliche at this point. I didn't love the look-how-fabulous-humans-can-be-if-we-all-just-get-along because it's not untrue but it's boring. Or more precisely it's idyllic but it's not an ideal that I find appealing or interesting. I didn't like the parts where the characters were all “I'm annoyed at him for trying to hold onto hope” because hope is a beautiful thing and especially when you're creating desperate stories like this, it's the thing characters should hang onto, not resent. Most of all I didn't like the cheating logic.
For starters, I knew it was the Centauri crew midway through the first book. So that wasn't a surprise. But that one was ok because it made since. Even with the feint (I guess in case anyone had guessed that) with the “they're really aliens! they have blue blood" misdirect. But wait they really ARE the Centauri crew. Who definitely didn't time travel. They just got in a storm that moved them forward and backwards in time. Totally different thing. Like, after all the build up, come up with a different explanation or own the one you've got.
And I suppose it doesn't help that I've recently read Brandon Sanderson. And while the characters in Undying are better than anything he's come up with thus far (and by that mean that I've read by him) his payoff has yet to disappoint. This payoff isn't terrible but feels a bit sloppy and cheap in comparison. That being said, I did REALLY like Dex especially in the first half of the book and the dimension he added. He became a bit less interesting toward the end but the pivot with him finally engaged me in the story in a way I hadn't been through the beginning and kept my attention into the second act. The hard thing is it's not any one thing that ruined the book for me. It's a lot of little things in an otherwise decent book that I didn't love.