Bleeding Cook's Pedro Bouca gives us an excellent Dylan Dog 101.
Well, Dylan Dog is the most important Italian comic character of the last thirty years or so. Created by the brilliant writer Tiziano Sclavi, then at the service of the Bonelli publishing house, which is still the series' publisher, the comic had many revolutionary characteristics when first published. Due to the similarities (they are both London-based supernatural investigators), we could call it the Italian John Constantine (Dylan Dog appeared later, in 1986, but starred directly in his own solo series, well before Hellblazer), although, of course, they have many important differences.
Dylan Dog was a sensible kind of hero unlike most of the Bonelli roster at the time. Famously inspired (visually at least) by the actor Rupert Everett (who also starred the Sclavi-written movie Cemetery Man, whose protagonist has a lot of similarities with Dylan Dog) he was hardly the decided, two-fisted hero like those that made the publisher famous and as such he stood out among his peers much like Peter Parker did when first created.
That wouldn't account for much if the stories themselves weren't interesting, but here Sclavi's talent shone brightly. An incredibly creative writer, he wrote most of the series' first ten years (no small feat considering that it's a monthly 96-page comic with many additional special editions with even larger page counts) and was at the same time able to breathe new life on hoary old horror clichés like zombies and ghosts and to create wild new horrors for Dylan to face, from surrealistic hells to more mundane (yet still chilling) terrors like serial killers. A lot of his work defies description and he even admits that some of his stories (like the US-published story Morgana) are incomprehensible even to himself!
Considering that linear, utterly conventional storytelling had been (and still is) the Bonelli staple for years, it's easy to see how revolutionary the series was at the time. Sergio Bonelli himself famously said that he couldn't understand the series' appeal. And the public followed. Initial sales were reportedly in the 40k range, unimpressive for the time, but the title gained sales rather quickly and at its prime in the early 90s the character was selling a million books a month! For a short time it was the best-selling comic in Italy, beating longtime sales champions like the cowboy Tex and Topolino (Italy's Mickey Mouse comic). With time it lost ground and newsstand sales are now just a bit over 100k.
The decline may be explained by Sclavi's absence from the series. His output diminished after the first decade and completely stopped after the second. He is mostly a novel writer nowadays and doesn't seem at all interesting in getting back to the monthly grind. He was, however, followed by a string of talented creators who have left their mark on the character, particularly Claudio Chiaverotti (who has been busy with his own comic characters lately) and Paola Barbato. The character's current main writer (and editor) is Roberto Recchioni, an Italian comics rising star who has famously headed a big character reformulation about a year ago. The jury is still out on that one, but after an initial resistance by the old fans, the "new" Dylan Dog seems to have breathed new life on the hero.
The character has also been published in the US before. In 1999 Dark Horse tried to bring the Bonelli comics to the US publishing 6-issue limited series starring three of their characters. Established US artists did new covers for them. Dylan seems to have been the most successful, certainly boosted by the beautiful Mignola covers, but the line as a whole was unsuccessful. Dark Horse tried again in 2002 with a one-shot issue (this time keeping the original Italian cover) and yet again in 2009 with a thick Omnibus compilation of the seven previously published stories, possibly to tie with the movie then in production.
Movie? Yes, there is a Hollywood Dylan Dog movie out there starring Brandon Routh. Please, don't watch it. Cemetery Man is a better "Dylan Dog" movie than that.
There was, however, a big difference between the US-published stories and the Italian originals. In the original comics, Dylan Dog's sidekick is Groucho, an unemployed actor that looks, thinks and acts like a Groucho Marx character! He is responsible for most of the humor in the series, but Dark Horse seems to have feared lawsuits from the late actor's estate. The character's appearance was changed and he was renamed Felix. Epicenter has yet to reveal what will happen with Dylan's longtime partner.
All the Dark Horse-published stories were from the early Tiziano Sclavi years. Epicenter has yet to announce if its stories will be from that period, the middle "Sclaviless" period or the recent reformulation. With more than 400 stories to choose from (350 from the monthly and some 100 or so from the many spin-off books), Epicenter has an embarrassment of choices ahead of it! No matter what they choose to publish, though, it will certainly be good.