Waiting for a Sequel

I dislike waiting for sequels of books. I feel like it's a massive publishing company scheme. I have a couple of series that I've started, but I am waiting for the next book to come out in the fall. When of the series is the sequel to "I am Number Four." The book was quite good. It's about a young adult that's an alien try to pretend to be human to avoid being killed by an enemy race. The movie was disturbingly a little different than the book (and the book was even better). I can't wait for the next one to come out. My friend recommended the book to me. What books would you recommend to read over the summer?