Instead of being a monster film, like I might expect from del Toro, this is really a classy gothic. Sure, it has ghosts, pretty creepy scary ghosts, but it really has more in common with Gaslight or Hitchcock's Rebecca. Still, it hits the two Hitchcock high "Cs" hard and strong: Classy and Creepy.
Edith Cushing is ten years old when her mother died, and then visited her as a ghost, warning her about "Crimson Peak." More than a decade later, as an aspiring writer, her life is turned upside down by falling in love with Baronet Tom Hiddleston (which I'm sure happened to many a girl) and her father tragically dying. She marries Tom and moves into his estate, which she didn't know was also called "Crimson Peak."
Every frame of this film is exotic and full of life. It is simply beautiful or powerful. The casting was amazing as well, where Mia Wasikowska is perfect as the doll-like woman attempting to be frail for her husband, but is really strong. Tom Hiddleston is the frail man attempting to act strong and Jessica Chastain is simply creepy in every scene. I think it is a misnomer to call the film a "horror" at all. It isn't even a "thriller" because there is little surprise in how the plot turns out. But as a gothic (with horror elements), it is expertly measured, and a visual feast.