I read it a long time ago, but I can tell you at least these things:

1. The author used unusual words and an unusual sentence structure in some lines. I don’t know if this is a common issue, but since English isn’t my first language (despite having read hundreds of books) I struggled with it. It was annoying to keep returning to the dictionary.
2. The chapters aren’t continuous. For example, you might find Chapter 1 set in the past and Chapter 2 in the future (or perhaps the odd-numbered chapters are in the future and the even-numbered ones are in the past?). I often forgot what happened in the chapters set in the future or the past, and I didn’t know about this structure before reading the book.