If you wanted to read a book about loyalty, then Midnight Tides would be my recommended choice.
The feeling you get with Midnight Tides is like: 'what am I reading?' It's a completely different story course from the initial merging twin plotlines in Genabackis and Seven Kingdoms.
Everything is new. There are more characters to get into and new locations to memorize. The background is still the same, though, as you get to see from the second half of the book.
Midnight Tides is a lengthy read, and not just in the word count. The newness of the plot coupled with the unique complexity employed by the author in writing means that you have to take it real slow to understand any of the happenings.
You only begin to understand a somewhat new magic system towards the end of the book as you realize it was very much similar to that of preceding books. Some loose ends and threads connect with the main plot at the end of the book, and the entire thing keeps expanding. It hasn't stopped expanding yet. There are new characters, histories, mysteries, plots and schemes, and worlds. It's terrifying in its complexity, and you almost heave a sigh of relief when things become a little clearer at the end.
Midnight Tides would be my least favorite in the series so far due to the especially complex writing style, but it's still a 4/5 for me.