Had never seen this classic Vincent Price vehicle until last night, and I found it to be the sort of good, old fashioned creepy fun that the Merchant of Menace is famous for. As others have pointed out, many of Price's performances have a wonderful, jocular quality that lets the audience in on the gag, so to speak, and House on Haunted Hill is a superlative example; in fact, it contains numerous instances of characters breaking the forth wall and directly addressing the viewer. Needless to say, Price is totally in his element here, and clearly has a lot of fun with the role, as he always does.
As luck would have it, this turned out to be an ideal movie for me to watch whilst still hungover (not my original intention, you understand). The exposition is laid on nice and thick (and not in a bad way, for a change), and, due to the general set-up, often takes the form of mini ghost stories, which the actors, and especially Price, deliver with relish. Furthermore, like many haunted house romps, the plot is essentially a springboard for what later becomes largely an exercise in atmosphere and pure effect. Which is all basically a long winded way of saying that you can take the narrative or leave it, hence why it makes for a good hangover film. Not that the story is bad by any means though; it ingeniously blends elements of the Old Dark House and murder-mystery/whodunit sub-genres, and keeps twisting and turning until the very end.
It seems that Alfred Hitchcock was very impressed with the success of this low budget shocker, as it apparently inspired him to make Psycho the following year; and William Castle would reciprocate this highly flattering act of imitation the year after that, with his homage to Hitch's classic, Homicidal.