A few thoughts: Who could've guessed Mario Bava - director of some of the moodiest and most visually groundbreaking horror movies of all-time - would make one of the silliest sci/fi films I've ever seen. But this is by no means an insult. Being a Bava film, obviously the sets, lighting, and cinematography are wonderful. With tons of fog and brightly colored lights shining on strangely shaped background objects, this very colorful and imaginative scenery helps make every frame of this movie just fun to look at. The costumes are goofy full body suits with stripes (sort of like Tron without the lights), adding to the campiness this sci-fi/horror/fantasy already has in spades. A sort of vampire/body snatcher/zombie hybrid set on a bizarre planet, this is one of those catchy movie titles that doesn't at all disappoint. Much like with 'Hercules In The Haunted World', Bava knew how to deliver on a promise. No, it isn't a particularly scary or creepy movie, with the sci-fi/fantasy aspects definitely taking precedence, but with all the awesome visuals and cool atmosphere, it never felt lacking to me. I wouldn't change a thing about it.
Who would I recommend it to? Anyone who can appreciate fun and very visually-centric sci/fi fantasy. This is Bava at (arguably) his most aesthetically creative.