(found at library)
It seems that people who create superheroes (for comic books, especially, but also for TV and movies) are interested in characters who go against their inner nature to become something else. Thus, you have Angel, the vampire with a soul; Spawn, a dead guy who somehow gets out of Hell to avenge something ... I forget (one antagonist in this series is apparently an angel who's hunting him down because, well, he's from Hell); the Iron Giant, a weapon who wants to be Superman; and finally Hellboy, some sort of demon brought to earth by Nazis to fulfill some nefarious plot, who turns against them and now works for the U.S. Bureau of Paranormal Research and Defense. These two books were at the library, so I checked them out, but since they're not at the beginning of the series (nor even next to each other in the sequence) I get that there's some plot points and character origins that I'm missing, like who Abraham Sapien (the amphibian?) is.
At any rate, the artwork is excellent—Mignola uses a lot of black and greys, the page layouts are very interesting and often contain panels in which it appears nothing is happening, but they do a great job of pacing the story, and setting the mood. Somehow his style manages to make everything look both 2-dimensional and solid: the style reminds me of WWII propaganda posters, but with more substance. I can't really explain it; you'd just have to look at one. The writing is interesting—like Gaiman, he draws from a deep pool of existing stories, myths, and legends (like the Russian Baba Yaga, with the house on chicken legs and flying around in a giant pestle) and creates something that conspiracy fans would love. Both of these stories involve present-day Nazis; I got the impression that they're common in the series, as well as Rasputin, who's still somewhat alive and trying to bring about the end of humanity.