I've read all the Birthright books (I think). The first two The Iron Throne and War by Simon Hawke are okay but a little dry but I can't remember enough to give a good synopsis. I think the second one has to with the power struggles in the Anuriean empire after the death of Micheal Roele, but whether its right after the first book I can't recall.
I liked the other books better (The Spider's Test, The Hag's Contract and Greatheart).