This started out very promising for me. I started this book while running on the treadmill and it kept me entertained enough to break my record.

However... My main problems with this book are pacing and the ending. Also, the science veered into a direction that kind of ruined it for me.

First, around maybe halfway the story became a bit of a slog. The plot was interesting but when it wasn't moving, I got bored. The book started with a mystery element that was ignored until the very end. That was disappointing. Why do you dangle that in front of me, just to make me finish the book? (It did work though)

Second, the ending was rushed with a character just coming and telling everything that happened to her and solved the plot like that. It was so disappointing.

Third, the science. Every time the word "quantum" is thrown around I'm immediately skeptical. When the book went into the quantum realm, I couldn't suspend my disbelief anymore.

I'm not an expert in quantum physics, absolutely not, but I found this plotline too hard to believe. Also, quantum physics are a great way to explain anything and everything because we don't know how it works, especially us laypeople. So for me it was a lazy solution.

There were some points that I couldn't get over - like what it is to observe, looking at things? Can the quantum realm interact with the physical world or not? Why do the ghosts of those in the quantum realm be observed for just a small time? Why can they be observed (aka seen) at all? Why is one character able to stay in the physical world for so long? Why can the rose be seen and smellled when it should have, according to the book's own logic, disappeared?

Slowly the book started to bore me and even annoy me. I had to force myself to finish the last 30 pages or so. Still, there was so much that I did enjoy that it's 3 stars from me and I'm planning to start The Three-Body Problem next.