A few thoughts: A William Castle study in fear...and it's every bit as fun as you could hope. Vincent Price gives one of the most entertaining performances of his career, which is a statement I don't take lightly. Watching him in this movie fills my heart with joy, and if it weren't for how much I enjoy the silliness of the story, he would totally dominate the whole thing. The movie is about scientists trying to discover what causes the tingle that goes up your spine, and the conclusion they come to is that it's a monster that lives inside of you that appears when you're scared, and only your screams can keep it at bay. It sounds ridiculous, because it is ridiculous -- ridiculously fun!...but seriously, this movie is an absolute blast from start to finish. I love Castle's opening, the way he allows Price free reign, the corny concept, the creature design, and the totally awesome scene with controlled use of color. It's one of my favorite movies of the 1950s, and a weirdly overlooked movie that would be a ton of fun to screen for Halloween.
Who would I recommend it to? Anyone who likes their classic horror with a sense of humor and a nice blend of fantasy and science fiction.