Recommend some Batman comics for a six-year-old

A friend's child is suddenly obsessed with Batman. So I'm looking for some recommendations for Batman collections that would be suitable.

Interesting Links for 19-04-2014

• A fascinating finding on the relationship between male parental age and psychiatric problems.
  (tags: men children mentalhealth )
• Transcendence: A Movie Too Terrible to Even Hate-Watch
  (tags: movies johnnydepp review epicfail )
• 20 lies parents tell their children
  (tags: parenting lies )
• Proving and Quantifying Sexism.
  (tags: sexism science )
• Impact of childhood bullying still evident after 40 years
  (tags: bullying )
• Your brain send current information and memories locations over the same pathways but with different frequencies
  (tags: brains memory )
• How Russian legislature just made lives more difficult for Russian bloggers
  (tags: blogging russia livejournal media censorship )
• Is Ukraine's Donetsk region the next Crimea? Well...
  (tags: ukraine russia )
• Gorgeous photography. I love getting these on my friends page
  (tags: photography beautiful )
• Lilo and Stitch deleted scene!!!
  (tags: disney hawaii )
• The truth about Jesus and Easter
  (tags: jesus xmen funny easter )