This picture contains a few nice atmospheric bits, but nothing much happens. There's very little tension, and what there is comes only at the very end.
More could have been done with the mythic Greek elements of the story, rather than falling back on Edgar Allan Poe's "The Premature Burial". I'd recommend this picture only to hardcore Karloff fans and aficionados of Val Lewton (although many Lewton fans agree that this is one his weaker pictures).
Definitely not one to keep you on the edge of your seat, but not exactly boring.
One bit doesn't make sense. Karloff comes to the island with the journalist, and then destroys the rowboat to keep everyone from escaping. How did the rest of the people get there? Well, let's assume he wrecked the other boats, too, although one of the characters says, "He's wrecked the only boat on the island!"