Dracula acts more as a permeating force throughout the series than actually being a physical threat. The same goes for about three quarters of the book.
Dr. Seward uses a phonograph, which was a novelty when the original book was published.
"Children of the night, what music they make" is a reference to the original Dracula (1930) starring Béla Lugosi, as the Count says "what sweet music they make" in the book.
The characters Dracula, Professor Van Helsing, Mina Harker (née Murray), Dr. Seward and Renfield all have a role in Penny Dreadful. Jonathan Harker is only mentioned.
Major differences/liberties taken from the original book:
Dr. Seward is American in Penny Dreadful. The only American in the original was a Texan man called Quincey Morris.
Renfield is Dr. Seward's secretary in the series. In the book, he's an assistent to a real estate agent that gets touched by the evil of Dracula and goes insane in the process, leaving him with a constant lust for the blood of small living creatures.
Rather than fully fledged vampires, the Dracula of the series seems to be more reliant on an army of vampiric minions, similar to Renfield. In the first series, the party of heroes is attacked by more "traditional" fang sporting vampires. In the book, there are only five vampires: Dracula, his three brides, and Lucy Westenra. While Mina Harker is portrayed as a vampire in multiple films and series - including Penny Dreadful and The League of Extraordinary Gentlemen (2004) - she's never fully turned into a vampire in the novel.
Professor Van Helsing only plays a small role in Penny Dreadful. In the book, he leads the "pack of hounds after the fox", as the human protagonists travel far and wide in pursuit of The Count.
Strikes the perfect balance between Gothic art-house horror and gory B-movie action; visuals look great
Well, I'm trying to write a completely spoiler-free review here, but I guess it's safe to announce that 'Penny Dreadful' looks positively gorgeous. Great production design and cinematography: by the time we get to see Victorian London as night descends upon the city and the fog starts creeping through those narrow cobblestone alleys, nearly every frame looks like a beautiful, Gothic painting (and not once did I spot a fake looking CG-background). As far as the actors are concerned, they portray their obscure, troubled characters with a certain kind of "theatre" intensity that fits the story and the turn-of-the-century setting very well.
Story-wise I don't want to give away anything but of course, there are unholy things lurking in the shadows that need to be fought (and they look rather convincing: the make-up effects are another strong point of this show). Like the iconic "Hammer Horror" films of old (usually starring either Christopher Lee or Peter Cushing or both), 'Penny Dreadful' draws its setting, characters and general inspiration mainly from some famously dark tales written by Mary Shelley, Bram Stoker and Oscar Wilde (and to a lesser extent from sir Arthur Conan Doyle's Sherlock Holmes stories). And just like the Hammer films - who may seem rather tame now but were shockingly violent for their time - this show is neither for purists of said literary works nor for the faint of heart.
While some scenes are genuinely scary in a tension building, "old school" kind of way, we also get blood soaked action sequences that will probably put off some viewers, but seem entirely appropriate given the show's title (in the 19th century a "penny dreadful" used to be a booklet of cheap, sensational fiction printed on pulp paper which could be purchased for - wait for it: a penny).
My overall verdict: 'Penny Dreadful' dishes out a hefty mix of gory violence, classic horror creatures, sex and action, but it never forgets to build atmosphere. The B-movie elements are undeniably there, but they're deliberate (the title says it all), and this is by no means a cheap affair. Beautifully crafted and with a great cast, I strongly recommend this show to anyone who likes the old "Hammer Horror" movies as well as films in the vein of Tim Burton's 'Sweeney Todd' and 'Sleepy Hollow'.
But not just for the fans of "Goth Horror" is this well worth checking out; I would say that after 'True Detective' and perhaps 'Fargo' this is one of the most promising new TV-shows of 2014.