Here is a quick description of the story from Amazon's book site:
The body of a young girl is found mangled and murdered in the woods of Hemlock Grove, Pennsylvania, in the shadow of the abandoned Godfrey Steel mill. A manhunt ensues—though the authorities aren’t sure if it’s a man they should be looking for.
Some suspect an escapee from the White Tower, a foreboding biotech facility owned by the Godfrey family—their personal fortune and the local economy having moved on from Pittsburgh steel—where, if rumors are true, biological experiments of the most unethical kind take place. Others turn to Peter Rumancek, a Gypsy trailer-trash kid who has told impressionable high school classmates that he’s a werewolf. Or perhaps it’s Roman, the son of the late JR Godfrey, who rules the adolescent social scene with the casual arrogance of a cold-blooded aristocrat, his superior status unquestioned despite his decidedly freakish sister, Shelley, whose monstrous medical conditions belie a sweet intelligence, and his otherworldly control freak of a mother, Olivia.
At once a riveting mystery and a fascinating revelation of the grotesque and the darkness in us all, Hemlock Grove
has the architecture and energy to become a classic in its own
right—and Brian McGreevy the talent and ambition to enthrall us for
years to come.
While the television version of shows often stray (for example, Vampire Diaries), that may be less likely here since McGreevy is an executive producer on the series. McGreevy is a screenwriter turned author who knows the process and wanted to share his story via a long term series rather than a two-hour movie.
And while the original plans were to film much of the show in Pennsylvania, keeping it close to the storyline, this fell through because of tax issues. Hence, the series will be shot in Toronto was some scenes being filmed in Pennsylvania. I know that some of the show was being filmed in Toronto's Casa Loma on November 23rd, which is an impressive setting. And the town of Hemlock Grove will now be represented by Ontario's Port Perry just north of Toronto.
Hemlock Grove's cast includes actor Landon Liboiron (Terra Nova) as Peter and Bill Skarsgard (brother of True Blood's Alexander - so there is a vampire connection!) as Roman. It seems that Netflix was able to save one of the actors from Terra Nova even it it was unable to save the show itself.
You can learn a little more about the McGreevy and the book in this Wall Street Journal online book review. And here is a clip of Eli Roth, who is the director/executive producer of Hemlock Grove, talking about the show and the role of Netflix.