George Zucco, whom I had never heard of until now, stars as a kindly doctor and his evil twin brother who is hell-bent on Satan worship, and having a hunchback assistant (because you need that). His Satan-worship even seems to make him immune to death! You might not find some aspects of the film to be original. I mean, a hunchback? And the good twin and bad twin dichotomy? Nothing new there (though newer in 1943 than today). So put this one on the pile with all those other films...
But wait! Whoever provided the imagery really cared about the scenes they wanted to show. The opening is one of the more powerful scenes you'll find in a film of its era. A book called "History of Vampires" burns slowly in a fireplace (forshadowing the later destruction of the occult book collection) while a super-imposed face speaks to us from beyond the grave.
Yes, you'll have to be tolerant of older films with no color and the less technologically advanced filming procedures. If not, you might be snoozing in a matter of minutes. But true fans of the old days will enjoy this one and all the way to the end you may not be able to guess which brother - if either one - will survive this epic battle of good versus evil.