It is not, contrary to marketing you may have seen, a horror movie. It is a GOTHIC ROMANCE, which means that it's a romance plus a mystery, all surrounded by doom and decay and peril. And ghosts. And EVERYTHING IS TURNED UP TO ELEVEN.
Which is why it works, I think. The movie knows that it's a melodrama, and doesn't shy away from it. So the costumes are lush. The violence is gruesome. The decrepit old mansion is falling to pieces. The ghosts are both horrifying and scary. Everything is just... heightened and intensified. Which is why you have to say the name in all caps: CRIMSON. PEAK!
It's also got a whole lot of details where afterwards you go "oh, did you notice this thing? I thought that was really clever/well-done/surprising/neat!" It's a very well-constructed movie.
So I definitely recommend it.
(...Unless you have an aversion to butterflies, moths, ghastly injuries, or large quantities of red liquid, all of which feature quite prominently in the movie. Yeah.)