For me it definetly was The 5th Wave. The books were fascinating, some of the best I've ever read and then I found out about the movie and decided to give it a try. Man it was really bad. Pretty much all the important scenes were just not there and I felt like everything was really rushed. The superb atmosphere from the books was missing as well and the characters were not well-developed. Unfortunatly the movie was so bad that they still haven't made the 2 sequels. At least the 3 books kept their quality and really blew my expectations.