The Diary of a Young Girl - Anne Frank.
This will definitely be one of the best books I have ever written and unbelievably as the world knows - written by a teenager. They are rather her letters precisely dated on which day she has written for almost two years of her life from the age 13 to 15 - hidden behind a book case somewhere in Holland during holocaust.
Also, this will be one those rare books I actually dreaded to end (Unlike ever in the past) because we all know how its going to end. Its simply superb the way she has written those letters, the way she grows up during the writing, her opinions, happenings everything so very well recorded. At one point I actually wished I could take her out of the book and give her a tight hug and a kiss on her dimpled cheeks - its so rivetingly written. Unfortunately this one was an extended version that I had got and was in great details too.
If you haven't read this yet - you've got to pick up like NOW and read it back to back. Again it was simply unputdownable and I finished it in flat two sittings.
I am going to make this a mandatory read for all the teenagers I know starting with my own daughter in a couple of years. The Diary of a Young Girl