Batman: The Long Halloween - Jeph Loeb & Tim Sale
I've always liked Batman; something about being a superhero without really having supernatural powers makes him a little more down-to-earth (although he is a multi-millionaire, which is a little out of reach). This book is a collected series, from one Halloween to the next. It's got gangsters, a whole collection of classic Batman villains, and a pre-Two-Face Harvey Dent. There's also "Holiday," a mystery serial killer who has been killing on one holiday per month, and there are several viable suspects.
Some of the gangster stuff is a bit cliched, of course, but pretty much anything gangster-related is going to have similiarities to the Godfather movies. And I'm not sure I liked this particular artist's style as much as some of the others. The overarching storyline, the mystery of the Holiday killer, and the holiday theme itself kept me interested.