Quick-take: I believe nothing.
Absolutely nothing in this book is believable.
Sage is now king, but he is worried about pirates along with a hostile nation starting a multi-front war. With all the resources of the kingdom, what does he do? Everything on his own.
From the initial failed assassination attempt, to him singlehandely saving his country, I cannot believe a single line of text. Where are his troops? None available. Where are his advisors? Scheming against him. Why is he able to travel a few hours on a horse and reach another kingdom and king? He travels another evening and reaches another kingdom and king. This is all under disguise relying on no connections. Are kings really that accessible? Is his world really that small?
Every cockamamie plan seems to work out. His ideas are terrible. Fortunately, important recurring characters emerge in places they have no business being in, yet it is very convenient to the story and Sage's ideas that they are there.
Sage's skills of persuasion rivals the infamous stories of Alcibiades. Sage's threshold for abuse and ability to survive rivals Rasputin.
Finally, at the very end, everybody clapped.
It's like somebody took book 1 and made fanfiction for book 2.
Score: 2/5. The story was at least fast-moving. I am picking up book 3 because it is the last.