The problem I have with Franco films is this: they're full of beautiful naked women that really don't do much but lounge around. An erotic film should have something remotely akin to a sexual encounter. Even in 1969 they could that, especially in Europe. Well, there is some minor lesbianism in a scene or 2, but....
I'm not going to get into plot details because few people in this film's crowd are interested in sitting through this to critique the plot. If it's truly based on a De Sade work then great, but from my experience a De Sade tale honestly transferred to film would in reality be nothing less than XXX rated (and in some cases a snuff film). So clearly there are elements missing from this flick in the translation from book to movie, as it's not pornographic. Just a PSA to De Sade literary fans.
Franco--with his total of 3 movies bearing the "Eugenie" title--gives De Sade a bad name, believe it or not. The books are much better, and not as tame as Franco makes them out to be.
However, compared to his contemporary Jean Rollin (who was comfortable making the occasional porn film, as it happens), Franco certainly had decent budgets to work with and clearly used them well. He gets sexy actresses, and nice movie sets which fit the story. His direction isn't pedestrian, but he must have skipped school on the day that really important filming techniques were discussed, such as keeping the audience engrossed with the characters. So he decided to make up for that by parading nude women around, and I will definitely not complain! It's always a plus when a film has nudity with a purpose, and I think Jess Franco typically manages to provide that purpose.
"Justine" is probably the highlight of his career, but this particular Eugenie film, overall, is actually pretty entertaining. Not something you'd want to watch again and again, but one that you'll find yourself wanting to pull out of the shelf on occasion.