Here would be one of the best Introduction to the Subject.
-The last laugh ( just one of the best and as much for the Joker as Batman and Gordon)
-The Haunted Knight ( ok but an introduction)
-The Long Halloween ( An inspiration for the last 2 film, key word is inspiration)
-Dark Victory
-HUSH ( MMmmm that one is so good it’s like candy dip in syrup)
The last 4 Graphic Novel are kind of a serie but take that loosely
-’‘All-Star Batman and Robin the Boy Wonder’’ I think arround 13 issues are out. It’s Batman for Adult and as BadSorryBarb as it can get!
Everybody recommend ‘‘The Dark Knight Return’’ but that is so not an introduction but more hardcore reading. It answer’s pretty well why Batman is more dangerous than Superman.
-Batman / Superman “Public Enemies” and
-’‘The Supergirl from Krypton’’ are prett good and give you a good conterpoint.
That would be my introduction recommandation. There is way more cool stuff and I probably forget a lot a seminial work but those recommandation are not to much grouded in ‘‘continuity’’ so it’s easier to understand base on a comon knowledge of the caracter.
Good Reading!