A few thoughts: I've been pretty clear in the past that I'll watch anything with Peter Cushing in it -- he's my favorite actor, after all. So, naturally, I went digging into some more obscure stuff of his and came across this one. So being the Cushing fan I am, even the lousy script, nonsensically exploitative subject matter, and campy presentation couldn't take away from the joyous experience of watching my favorite actor let loose and give a totally unhinged performance. Aided by an equally psychotic performance from Sue Lloyd (who miraculously manages to hold her own beside Cushing), this is not a movie you watch for anything other than the acting. It's gory, stupid, has a pretty distracting swingin' '60s soundtrack, and doesn't care even remotely about telling a good story. But still, thanks to these two leads, it manages to be entertaining in its own right. Mix in some pretty disturbing and intense scenes with a whole lot of tooth-gnashing, and this is what you get. I cold never say it's good, but I certainly wasn't bored. Also, it's got a hilarious poster.
Who would I recommend it to? Imagine a more crazed Dr. Frankenstein (Cushing) in a Herschell Gordon Lewis movie. If that sounds interesting to you, give it a try. If you don't know what that means, just try something else instead. You're not missing much.