The authour mentioned in the acknowledgedments that he initially thought up this book on its own with an authour friend of his. I feel like this explains a lot of the annoyance I felt while reading this book. Because during this book I felt like the plot points where very far fetched and unlikely to happen in this series with this character being the way he was in the last four books. In the acknowledgments the authour also mentioned that his editors had to remove a lot of repitition and plot holes is his book. Which to me explains my other annoyances with the book, the fact that a lot of the concepts of the last few books had to be reexplained and that I noticed some plot holes. 
Putting all that aside, when I didn't focus on my annoyances too much, this was still an okay book. I hope the sixth book will redeem this series again for me, as this fifth book was quite a dissapointment to me.