The theme of this series seems to be indignation. Every significant character screws the protagonist over at least once. I would guess that she suffers major betrayals at a rate of four or five per book. When she finds out, she generally cries a little, and the character in question explains that he's very, very sorry. No revenge is ever extracted, apparently because she's not the sort of person who would do that. Eventually she forgives him, mostly. The story continues on.
For a while I was convinced this was just a phase: the main character is initially a nice person, and then after getting backstabbed a couple times she starts pushing back. But I read through Book 3 hoping to find the point where she starts standing up for herself, and no standing-up-for-herself has happened, and I'm beginning to think it's not going to.
Quote from a review of Book 5: "She is faced with perceived physical violence, mental cruelty that evokes disturbing memories and emotions from her past, and efforts at intellectual and emotional control over her by nearly all the men who surround her. But along with her blossoming talents as a Queen, Lissa's enormous ability to forgive those transgressions by the people she loves only expands even further."
...So, I'm not sure what to say. I enjoyed these books for a while, when I thought the backstabbing was just a phase. Now it's looking like the main character is permanently engaged in a series of toxic friendships with manipulative assholes, and in retrospect I feel vaguely nauseated about the whole thing. But I gave this book four stars when I first read it, and I'm going to leave that rating.