There are things I quite like about it, but it's clearly a lesser film than the original.
The problem is simply that this human centipede will have twelve victims instead of three. (The third film will apparently have 500.) It's the obvious way to escalate things for a sequel, but in this case, more isn't better. Three is a good number. We got to know those three people. We could sustain our empathy even with the ones who couldn't speak. We had Akihiro Kitamura's final speech, which I've just discovered was written by the actor himself. In short, the victims mattered.
Here, that's not the case. They're just faces and bodies. We hardly ever even learn their names. Sometimes they get a bit of dialogue and we can tell they're unhappy about what happens to them, but that's it. Ashlynn Yennie is the main exception, back from the first film and playing herself. (The first film is fictional in this one and watching it is the main character's favourite thing in the world.) Yennie is extremely funny as the bubbly American starlet and then does pretty well shortly afterwards in a familiar role, but even there we don't really care about her. She's entertaining and we can recognise her. That's about it. There's no emotional connection on a par with the one she had with Ashley C. Williams last time.
The third act is thus just torture porn. Oodles of depravity, but it doesn't really mean anything except as an extension of the character study of our centipede-making hero, Martin. It's empty. We don't care about his victims, although we're still likely to be nauseated.
That doesn't make this a bad film. However it clearly makes it far less emotionally resonant than it could have been.
What does the film have instead, then? Answer: Martin. Our hero is Martin, a short, fat, balding, asthmatic man who's probably about fifty and lives with his mother. He has bulbous Peter Lorre eyes. Undressed, he's a disgusting sight. He also never speaks on-screen, although when excited he'll occasionally emit a squeak or burble. He's clearly got serious mental problems, presumably exacerbated by having been sexually abused by his father. Martin's harridan of a mother is bitter about this... no, not the child abuse, but the fact that her husband's in prison. She thinks it's all Martin's fault.
This is a man who masturbates with sandpaper and a copy of The Human Centipede. Whatever line you have for pathetic depravity, he's crossed it. Not only does he shoot people, smash skulls to pulp with a crowbar and collect victims for a recreation of the World's Greatest Work of Art, but his surgical technique involves hammers and staple guns. He kidnaps pregnant women, although in fairness he draws the line at babies. (Those he'll cuddle soothingly and then return to their car, seemingly not realising that the child's going to starve to death if he kidnaps its parents.)
He's the film's protagonist and a vivid creation. He's repellently compelling to look at, while both actor and writer/director are leaving no holds barred in their exploration of his childish personality. He doesn't like bad language. He's almost incapable of standing up to his mother. He loves his pet, which is a real centipede, and after building his human equivalent he displays a small child's love of things scatalogical.
The wholeheartedness of Martin's portrayal makes up for our lack of empathy for his victims. Not completely, of course, but it's still impressive.
This is an emotionally thinner film than its predecessor, for one huge and obvious reason, but there's still plenty of interest here. Martin is a memorable creation and there's thematic weight to him, e.g. the absolute failure of all authority figures in his life (including Dr Sebring) and the different ways in which the film's mirroring him with other children (the baby in the car, the pregnant woman). I see echoes of Norman Bates. I should also mention the ending, interpreted by some as "it was all a dream", but I think any simple reading leaves unanswered questions. If what we were watching was all a dream, what about the crying baby? If it was real, what about the one who escaped? Are the police on their way to get him, then? (That seems likely, since you'd expect Martin to be even worse at covering his tracks than Dieter Laser was in the first film.)
In many ways, I like it. It's set in Britain, for a start, and in black-and-white. (Tom Six did this because it made the film scarier and more atmospheric, but I'm more grateful for the lack of colour making the gore scenes less unwatchable.) The film's not just a remake as sequel, but instead is doing something new. It also settles once and for all the question of "which is worse, the middle or the end?" The end is worse. So, so much worse. It's just that it gets a bit repetitive once Martin's built his human centipede and is having his idea of fun with it. It's still a good deal better than its reputation, though.