I would be inclined to think Hitchcock made this corny film deliberately tongue-in-cheek if he had not all but disowned it in interview comments. Cheesy FX -- uneven performances -- but fine Gothic atmosphere and some great moments. Taken as it comes it is an enjoyable adventure a la Treasure Island -- except that Robert Newton plays the handsome hero!
Of course Laughton is over the top as others have said - but if you like Laughton you should see this film for his performance alone. Emlyn Williams also plays a delightfully sinister and menacing character -- I mistook him at first for Robert Newton (being prejudiced by the latter's subsequent typecasting).
Make sure you get the more recent Kino Video release (VHS or DVD) -- there was an earlier VHS version that was all but unwatchable.