You could start with 'The Dark Knight Returns'. It's a very influential graphic novel that shows an older, more grizzled Batman coming out of retirement. It has a lot of depth in terms of story and character, and it also influenced the Batman movies. Another option is 'Batman: Hush'. It has a complex mystery - based storyline that involves many of Batman's rogues gallery and also delves into his relationship with Catwoman.
For a new take on Batman, try 'Batman: Detective Comics #1000'. It's a celebration of the long - running series and has some great stories within it. It showcases different aspects of Batman's character and his world. Also, 'Batman: Zero Year' is a good choice as it re - tells Batman's origin in a modern and engaging way, with some cool new twists on the traditional story.