David Eddings is very good with political-fantasy writings. He looks
at politics from the point of view of warlords, citizens, theives, all
sorts of characters. He has many Ideas that can be adapted to a
Birthright setting easily. Also the Serpentwar Saga (the author's name
escapes me) is good reading, the second book is "Rise of a merchant
prince" and deals with economics and guild tradings wonderfully (a must
for rogue PC's)
-WMFII