You have to read the pervious books to really understand what is happening. There are some anatomy differences that are not explained in this book, although the human character knows about them.
The spacing of this book seems to take leaps, even though this entire book seems to be spaced over 2 days, maybe 3, the story somehow completes itself in that timeframe. 

There’s an overall storyline that doesn’t get finished in this book, that clearly continues throughout the series. Because of that, the ending feels incomplete and rushed.