I'll bite, though this may become my most unpopular post *ev-ah*.
I can't stand Laura K. Hamilton's Anita Blake series.
<<<<<GRAPHIC SEXUAL CONTENT>>>>>>
1) I don't like the MC.
2) As the series progresses, she keeps getting stronger. She begins as a reasonable character, but in each book she picks up new powers until she becomes some sort of super-duper-nigh-unkillable-freako-of-doom. I know that this isn't unheard of within the genre, but I think that it goes WAY too far in the Anita Blake series. There's just not as much suspense when the MC is the biggest, baddest mug on the block and no one can do crap about it.
3) As the series progresses, it becomes less about the MC's problems and more about her sex life. In fact, many of the problems that come up seem to be nothing more than shallow excuses for the sex scenes.
4) Speaking of sex scenes, in one of the books, she has TWO CHAPTERS devoted to ONE SEX SCENE and nothing else. The first chapter describes the man's body and the foreplay; the second chapter has the actual sex. There is nothing else in these TWO CHAPTERS. Why would you even do that? Why break a sex scene into chapters? WTF?!
5) Based on the descriptions in the books, you could list Anita's lovers by penis size. Generally, they get bigger as the books go on. She's with guy A, then guy B comes along, and Oh, My God, he's *even bigger*. Then comes guy C, and WOW, he's even bigger! And don't get me started on guy D...
Why is this necessary? And isn't it a little condescending? Which brings me to...
6) Everyone seems to get reduced to a series of apetites, especially the MC, who doesn't even like many of the men she sleeps with. That brings me to...
number 7, the summation: I get that the series is basically paranormal erotica, but I wish that there were more plot...I mean more action, but also more reason why she wants these guys around. Yeah, yeah, she HAS to have sex all the time and these guys are all great lovers, but the "I want to have sex with him/I want to kill him" dicotomy gets old after a while and there's just not enough of *anything* else. The series is all style and sex and no substance.
And, what about it do you think appeals to the mass market? Why do you think it has been so successful?
Sex sells. The series is edgy, and has a girl who is a necromancer/were-several-things having theesomes with Vampires and then splashing through bloody scenes and then getting it on with someone else. It has a strong female protag that doesn't get all sappy and weepy over things.
Several of my close friends passed this series around a bit (ERG...must...resist...snarky...pun...) and so I got to know far too much about it and even read portions. I also got to know what worked for those who liked the series.
One of those friends was skipping the sex scenes...then, at a certain point, he realized that skipping the sex scenes was basically the same as skipping the book...there was no more non-sexual action to drive the story (urg...drive...pun...).
OK, I have to stop writing now. Just *writing* about that series has got my mind in the gutter. And THAT, ladies and gentlemen, is why I think the series sells.