I really regret not reading this sooner. I received this arc one to two months ago but I got it at a weird time and it got hidden under the numerous other arcs I had been accepted for at the same time. The first time I did finally get to it, I didn't make much progress because the writing style is very funky, to say the least. So once again, I put it down to read other arcs.
I got back to it a few days ago and I'm overall, very happy that I didn't let it get forgotten.
The writing style was still very weird and required some a lot rereading before I could completely understanding what was going on. The first 3 - 4 chapters were extremely confusing. The writing style does get easier to read as you progress but I'm afraid that many other readers will loose interest before getting into the meat of the book, which is completely worth it.
My favorite aspect of this book is the awesome mystery. It's not a mystery book so to speak but it definitely has one. You ask a lot of question and every chapter leaves you with more questions so you just have to read one more chapter. And then another one. And then another one. You can't stop reading until, before you know it, you're turning the last page.
One of the huge downsides to this fast paced prose is the eventual loss of proper explanations.
The author definitely wrote this story in a way that made the reader ask a lot of questions. The narrator was as clueless (ok, a bit more clueless) as the reader was. By the end however, the reader is left with a lot of unanswered questions. I know what happened but why did it happen and how did it happen? We are left with a cheap "it just did" answer and that's the end of the book.
As I mentioned above, the main character was extremely stupid at times. He didn't see what was right in front of him. I understand why the author did that but I almost find plot-nesescary stupid even worse then just having a stupid character. In my opinion, it's a sign of shoddy writing. C'mon guys, I'm sure you could've found a better way to progress your plot than making your character a moron.
Callum wakes up with a feeling of amnesia because, well, his whole world is cray-cray. Instead of realizing that something is seriously wrong, Callum goes on for practically the entire book thinking everything is fine and he somehow forgot that he was a) an asshole, b) a football star, and c) the brother of a cripple.
Dude, that's not something you can just "forget". I can forget to ask someone a question. I can forget to do my homework. I don't go "Oh my god, I accidentally forgot that I have a crippled brother. Darn." That just doesn't happen.
The good thing is, besides that complaint, he was a pretty good hero. He didn't slut shame or act like a huge jackass to everyone. I did like him a lot, even though I did often want to slap him upside the head for acting like a huge moron.
This book really only had two characters of importance. While I don't think I can count that as a flaw because it fits the story, I would have liked Other Dimension Girlfriend to have had more of a personality other then that bitch.
One point of disappointment is all the wasted potential with some of these ideas. It could have been amazing if some points were delved into more. There were a lot of little things that were mentioned once and then never heard of again. These little things could have made the book so much better.
The ending is the main reason that UNDERCURRENT couldn't get a full 4 star rating. It was extremely rushed and underdeveloped. It felt like it should have been 10 - 15 pages longer with less of an abrupt ending.
UNDERCURRENT could have been amazing if not for a few points. I do recommend this book however. It's a pretty good science fiction story with an engaging plot that makes you want to keep reading. Overall, I'd say that UNDERCURRENT has earned the 
*
*please note, Benedict Cumberbatch has not actually given this book his seal of approval.
