I stumbled across this at a bookstore downstate, spine facing outward. When I picked it up and saw the cover, I immediately had second thoughts, assuming it would be just mindless fanservice like, say, Monster Musume...but it wasn't shrink-wrapped like that was. Besides, I already had it in my hand; immediately shoving it back on the shelf would've seemed suspicious. So I flipped through it a bit--yeah, there's fanservice here, but the main focus is weird horror, which is right up my alley. In truth, with all the gore and the not-infrequent nudity, it probably should have been sealed, but if it had, I would've missed out on a really enjoyable series.
The best way I can describe Franken Fran is that it's a mix of Petshop of Horrors and House, M.D., with more than a hint of Tales From the Crypt. In layman's terms, what we have here is an episodic series of (mostly unconnected) horror vignettes, with a heavy focus on the grotesque and the bizarre. All of them center on someone coming to Fran (or sometimes looking for the doctor who made her), for some kind of medical treatment, which always ends with a sickening twist. Some are better than others, but by and large, if you've go a strong stomach, and you don't mind a short-form format to your horror stories, there's a lot to like here.
The art is nicely detailed, and features the best-drawn "aberration"-type monsters (to steal a term from D&D), I've seen in manga, this side of something written by Junji Ito.
In terms of characters, the only two prominent recurring ones are Fran herself (a delightfully chipper, yet perpetually tired Frankenstein's monster-esque creation with incredible surgical skills), and Okita (a former patient of hers, whose head has been grafted onto the body of a house cat). There are a few other members of her Addams Family-style household who pop up semi-regularly, but they usually stick to the background. Thankfully, Fran is a likable enough character (as long as you're not bothered by her odd vocal tic of drawing out random words), and Okita is bizarrely chill and even grateful for what Fran's done to/for him. His character embodies an interesting counterpoint to all those whose lives are ruined by Fran's attempts to help.
As for the stories, like I said, they aren't all winners, but they are all memorable. From mob bosses, to millionaires, to average high school students, to creepy stalkers, there's a wide variety to the clients who come to Fran for assistance, so you'll never quite know what to expect with each tale. So long as you don't mind the lack of a larger narrative tying things together, Franken Fran has a lot to offer, in small chunks.
This series clearly isn't for everyone, but if you like your horror visceral, stomach-churning, and darkly humorous, chances are you'll enjoy Franken Fran. It's not all sex and fanservice, like the cover would have you believe.