This is very much like the question from May 6, 2010: "So … you’re halfway through a book and you’re hating it. It’s boring. It’s trite. It’s badly written. But … you’ve invested all this time to reading the first half. What do you do? Read the second half? Just to finish out the story? Find out what happens? Or, cut your losses and dump the second half?"
My answer from that question can be found here. As I said in May, FINISH IT! The only difference to my answer is that I am now better and stopping a book I'm not enjoying very early on so I don't tend to get to this point. However, if it's a book for my book club, then I will finish it no matter what!!