I ran across an excellent book by Lakshmibai and Brown called [Flag Varieties: an Interplay of Geometry, Combinatorics, and Representation Theory][1].  It seems like an excellent book for an algebraic geometer who is interested in representation theory and algebraic groups.


  [1]: http://www.ams.org/bookstore?fn=20&arg1=hinseries&ikey=HIN-40