Stephen King, totally awful, incredibly over-rated, long winded and just plain boring. I'm quite surprised he hasn't been mentioned already. In fact, about 90% of horror books are the most badly written tripe. Trying to get through one when you are over the age of sixteen is a nightmare for a whole different reason than the authors intended.
Tolkien, never saw the point, and I do actually really like the fantasy genre as a whole. I've tried to read LOTR a few times, even got to the beginning of the third book once, before realising that there surely must be more to life. Yawn...
My MIL reads all these David Peltzer poor abused me books. Totally beyond me, but she keeps trying to get me to read them too. Would rather stick hot needles in my eyes, quite frankly.
Would also agree with the anti-chick-lit brigade. I used to like it for pure escapism, but its really all so tedious and samey now.