Here's my honest (non-spoiler) opinion about Unwind and the books following it:
Okay let's get the bad stuff out of the way. To start things off, many times throughout the book (and Shusterman's other books), it feels really slow. I find myself trying to read a part of the book, hoping that something exhilarating will happen, but it turns out to be slow. I do not have a problem with a slow-paced book, but sometimes it feels too slow. Following that, sometimes things feel rushed. At some points of the book, I feel like some plot twists/reveals are too rushed. I would think to myself that it's a bit cliche. But otherwise, there's nothing else that really bothers me.
Now the neutral/mixed emotions. Firstly (and lastly), I have a love-hate relationship with Shusterman's character transitions. Sometimes the transitions are very good; making the audience know another character's POV at the time of an event. Other times... well it's a little dull. For example, one scene you'd be at an action paced-fight, the other, you'd be having a conversation. But yeah this is the only neutral/mixed emotion factor.
Now (the moment you've been waiting for), the amazing stuff. Where do I start with this? The characters are absolutely amazing, the plot is amazing, and the action-paced scenes are amazing (especially the one in the second book). I cannot use words to describe how much I love Neal Shusterman's unique way of writing. This is one of the best YA novels I've read. I'd go as far to say one the best books period. Thank you so much for your storytelling and literature Shusterman!