Reading your own book is something novelists must do over and over. After the first draft is written, here are the three ways I read to edit. I find a method whilst I am re-reading helps me to focus.
1. Character Viewpoint. Go through the text from each of the character's points of view. This might mean three or four different reads. In a long novel you can read each part that features that character; this will reveal inconsistencies or conundrums that you will need to look at, and make you work out what the character is doing between scenes in a bit more depth.
2.Theme. This focuses on the main theme. Read it again looking for ways to highlight or emphasise the theme. I also look to see if the theme is expanding naturally through the book.
3. "Person who knows nothing about it" read. This is the most important because you have to imagine you are a reader who knows nothing at all about the book or the subject. It helps me if I imagine another person reading it. Yes, you've got it - create another character in your head as dissimilar to yourself as possible and then imagine her/him reading the book.