Charles Bukowski - American author

Hi! My boyfriend's birthday is coming up in November and is a big fan of Bukowski. he mentioned a while back about possibly trying to find a first edition copy of one of his books. I thought that this would be a pretty cool gift to give him, but to be honest, I do not know to much about Bukowski. I know everyone's tastes vary, but could you suggest which book may be the best? I know he said the poem "Bluebird" was one of his favorites, I'm not sure if that gives you any clue. I appreciate your help, thanks!!