I really liked the dialog of this graphic novel. It feels real and keeps the plot alive. The characters get their own personality early on. They come "alive" very quickly. This reminded me of Sandman: Gaiman is definitely more erudite, but Vaughan has a stronger street-feel. 
 The art is good, very expressive. It's not super detailed, but it doesn't need to. It serves the story perfectly. Meaning, it actually communicates emotions that you wouldn't be able to express in words. I find this the best part of this book, the biggest accomplishment. It connect you with the characters -- how they stare into each other eyes, etc. -- and their story pretty deeply, and that's what a graphic novel is all about in my opinion.