Adventure, Aliens, Action: All in just a few books
The journey starts with I am Number Four and the book series is called The Lorien Legacies. They are a series of sci-fi young adult fiction books written by Pittacus Lore.
The series follows the journey of a group of adolescents who escaped as babies from an Earth-like planet called Lorien that is now near destroyed (aka. "in hibernation") after a war between the Loric people and the Mogadorians from a nearby planet named Mogadore.
The Mogadorians live to kill the Loric and the last 9 of their kind have been scattered all over Earth to go into hiding and emerge when the time came to fight for their fallen planet.
The series comprises three books so far, of a proposed six. The titles are I am Number Four, The Power of Six and The Rise of Nine.
There is also a list of supplemental books that accompany the series and delve deeper into the lives of The Lorien Nine. These are called The Lost Files. Titles include Six's Legacy, Nine's Legacy, The Fallen Legacies, The Legacies (which is actually a compilation of the first three but in a single book), The Search for Sam and Eight's Origin.
I've read all of the books and supplemental titles that have been published and I can tell you that they are very well written and it's extremely easy to lose yourself in the plot. I found myself finishing a book a day. I would definitely put them on par with The Hunger Games trilogy. I would explain more about them but the storyline is just so intricate and well-plotted that I'm scared of spoiling anything. So go and check them out for yourself. They're available from most bookstores and you can also get them as eBooks.
The next book, The Return of Lorien, is scheduled for release on August 13 2013. While the next supplementary title will be available on April 9 2013 and is titled: The Lost Files: The Last Days of Lorien.
If you aren't the reading type, you can always check out I am Number Four the film starring Alex Pettyfer, Dianna Agron and Teresa Palmer! (BEWARE: the movie is never as good as the book, just saying).