And yes, I have read the books. I actually read them while I was in labor, which might be borderline child abuse, but whatevs. I needed something to distract me from the horror of the situation - something that would not be intellectually taxing. And it worked, sort of. Judge me.
1) The writing is bad.
The most common criticism of the books is that they are badly written, and this is, in my opinion, absolutely correct. They are badly written. There is a lot of weird repetition of facts that are meaningless, and the main character, Ana, has a bizzare vocabulary that is by turns profane and outdatedly innocent.
Here is my impression of Ana, and the books as a whole. "Golly gee whiz I love being fucked inside out by my Sweet Fucked Up Fifty in the Audi. Then he makes me some English breakfast tea. Crap, he's hot! Just like how my tea is hot! Also, Audi! Hot!"
2) It started as Twilight fan fiction.
I personally don't think this is a good reason to criticize the books. Who cares if that's how they started? Lots of writers base their writings on familiar character prototypes and use cliche story arcs, and I don't really see that as much different. She didn't plagiarize. She just drew inspiration from the "awkward clumsy girl who doesn't know she's beautiful" and the crazy controlling boyfriend who needs to protect her.
3) It's mommy porn.
Again, so what?
I've heard lots of women say that they refuse to read the books because "I'm a married woman, and there's no place for pornography in a healthy marriage" , "It's a temptation fo sin" and blah blah.
Obviously this is subjective. We all have different definitions of what is sexually healthy, and we all have different limits on the amount of sexuality we are comfortable with in our literature, and we all have different levels of tolerance for the use of pornography within and without of our relationships.
For me personally, the books were completely and totally unsexy. The sex was graphic and kinky and plentiful, but I found myself skipping over almost all of it because it was A) not erotic and B) not interesting. So the pornographic element really didn't factor in for me, at all.
4) It is a negative and inaccurate representation of the BDSM community.
I'm conflicted on this one. On the one hand, I can see why members of the BDSM community might find this representation to be offensive. Grey is super creepy. And the notion that sadism/masochism are the products of childhood abuse, rather than a different iteration of normal human sexuality is a rather insulting one.
On the other hand, I never heard the author claim that Ana and Grey were supposed to be mascots for S&M. I don't see why they have to be representatives for an entire community. Can't they just be two fucked up people in a deeply unhealthy relationship?
Which leads me to -
5) The story is awful. This is a deeply unhealthy relationship.
This is indeed a deeply disturbing relationship. They are both drama addicts, and there is nothing healthy about them. Grey is controlling. Ana has no boundaries. They are both totally obsessive. Worst of all, it uses the commonly used but extremely unrealistic "magical vagina" trope, wherein a severely damaged and troubled man is "saved" by "that one special lady".
But again, I don't think this relationship was supposed to be aspirational. Sure, it's passionate, but that does not mean it's something to be emulated. And since this is a book written for adults, the readers should be mature enough to deduce that for themselves. It's an entertaining relationship, but its entertainment value lies in its dysfunction. No one wants to read a story where a man and woman meet, go on some dates, commit to be in an exclusive relationship, get married, have children, then die. Healthy? Yes. Entertaining? No.
The issues I have with the plot are more mundane. For instance, how does Grey have all this time to stalk Ana? Doesn't he have multibillion dollar companies to run? How is he able to take all this time off from work?
Also, why doesn't anyone tell Ana to dump Grey? Why is everyone ok with his creepiness?
And why the lurid fixation on child abuse? Icky.
In sum, I would have to say these books are pretty bad. The writing is awful, the characters are awful, and the characters are unrealistic.
That being said, they are entertaining, and they do keep you reading, if for no other reason than morbid curiosity. They will take your mind off anything awful that's going on in your life - like being in labor - and give your brain a chance to relax.
I would recommend them for intelligent adults who need a little mental vacation, who have good senses of humor. I would NOT recommend them for children, or adults who are inclined to take them seriously, or prudes.