If I'm being totally honest I'm not actually sure Penny Dreadful is any good. I'm pretty sure I really enjoyed it, but beyond that I'm a little hazy. The central conceit is of a period drama filled with reused fictional characters from that era alongside new ones, in a twistly and highly mannered sex-and-violence show against a lavish backdrop. So we have Sir Malcom Murray, father of Mina of Dracula fame, Victor Frankenstein and his Monster, Dorian Grey, and a few other cameos, alongside psychic/possessee Vanessa and bloody-obviously-a-werewolf-so-why-pretend-he-isn't Ethan, and Billie Pipers terrible accent. Yes, I know that last point is a bit of a cheap shot, but...wow.
Anyway, these characters maneuver around each other in a broad attempt to find Sir Malcom's daughter, but the show does suffer from a strange lack of focus, choosing to setup what are clearly future plotlines rather than stay on at the task in hand. Its like it can't quite chose whether to be a proper ensemble show, or a more story-driven show, and so sort of splits the difference. Sometimes this works, like the standalone episodes that give you an insight into this version of Frankenstein, or Vanessa's tortured past, and other times you're just left to wonder if they're ever going to just get on with it.
It's also got an odd attitude to sex - the Victorian Gothic tradition is steeped in the fear of the beastly act, and especially what it seemed to see and the untamed horror of female sexuality. Penny Dreadful is pretty loyal to this tradition, using sex as a transgressive and dangerous thing, often with bad consequences, especially for Vanessa, whose powers seem to be linked to her sexuality. In some ways it's fine; the show playing it in it's period where this sort of thing "fits" but without a counterpoint character (Dorian Grey doesn't count because a) he's underused and b) he's a man) it leaves the (almost certainly) unintended impression that the show itself buys into this nonsense just lurking off-stage.
What saves Penny Dreadful from all of this (and other sins) is the performances and direction. Timothy Dalton and Eva Green battle for dominance of their screen time with outstanding magnetism (at times I wasn't sure which I had a bigger crush on, which is an odd experience for a straight guy) and just sort of expand to fill any cracks the plotting leaves around. The rest of the cast gives it their all, but remain underserved by the story - Frankenstein and his Monster make a compelling pair but never really get enough to chew on, and Dorian, Ethan and Brona are...well, in the show for most of the episodes?
The set design, costumes and direction are also a stand out; something that is often raised as "faint praise" but here it is one of the things that allows the show to feel like it deserves its ranking as a prestige show. Along with the acting talent it means the show oozes quality and builds atmosphere and tension. Penny Dreadful was certainly worth watching, and was at times ridiculously entertaining for all it's faults. Hopefully it's already-commissioned second series will show a little bit more focus.