Mockingjay
I knew that the writing in this series wasn't the greatest. Structurally, the books are not all that interesting, and the world building is half-assed, and the prose is pretty lame. Still, I was taken by the first book because it had an interesting lead character and a fantastic premise. That premise held wonderfully for the first book, Hunger Games. The second book, Catching Fire, sot of offered more of the same, but not quite as good or fun. And then comes Mockingjay, a where everything shifts toward full on revolution. The problem is that the revolution premise is not that fun to read about, and worse still Collins' writing seemingly got worse as she went along. In fact, the writing is downright terrible. It became a total chore to read, and there were so many points where a piece of bad writing made me wince and I had to take a break from reading just to get the energy to continue. Mockingjay is probably the worst book I've ever read.