I wouldn't necessarily say they are the worst books I've read but at the moment I'm on the 3rd of the "50 shades" trilogy and to be honest I've not rated them at all.
They were so hyped and are not my type of book at all but I read them because everyone was raving about them, and people are referring to them as porn, but I think they are boring and tame. I've only carried on reading cos the first ends so abrupt that it's like reading half a book, I had to read the 2nd cos it was like ???? when it ended. But the 3rd is totally boring me now.