I did NOT read the Kindle edition, I bought it in paperback. This is not the end of the series, I already have the first in the next series.
Elle is just a wonderfully gifted writer, this series has been great fun and this was a great finale. Blake is finally reunited with her missing sister, Kit, who was taken when their parents were murdered many years earlier. It does go a bit above and beyond in the end when an SSA of a three person team, in an off the books investigation, takes down a LOT of Senators, Congresspersons and many others which stretches the imagination to the limit. However, the buildup is a reasonable investigation, thoroughly documented and the idea of a cabal like the Thirteen existing isn't out of reach. At all.
What I enjoyed most was the reuniting of the sisters, Blake's fears for what had happened to Kit were not realized, at least not in the way she thought. Kit was trained (in the manner of Hanna) to be an elite assassin, she's been in Seattle for a year because she refused an assignment to kill her sister. She, too, managed to gather an enormous amount of intelligence and evidence during her stint as killer for the richest and most amoral among us. I do admit the plot stretches credulity in that it revolves around a cabal that murdered three Supreme Court Justices in order to install three who would rule in their favor on issues that would benefit them financially. I mean the "bad guys" here are heinously evil. Not saying that isn't true but this level is, I hope, impossible. Still as a story it works. The sisters develop a relationship, finally deciding to trust each other and work together. Kit, though, then leaves, ostensibly to protect Blake because a kill order still exists for Kit and while they got most of the bad guys, they didn't get them all, certainly missed the biggest one of all who is still hunting Kit.
It was a very good series by a very talented author. I'm looking forward to reading whatever she does next beginning with the eighth book in this series and continuing with the new one she's developed and the Pax Arrington books as well. Kudos to her for her hard work and perseverance in getting her work out to an audience, a group I hope grows fast, she's well worth the time.