I would have to say my favorite book of 2009 was The Giver by Lois Lowry.
It is actually a book you would find in the "Young Adult". My daughter was required to read this book for her Pre-AP Language Arts class and I had never read it. I went ahead and read it so I would know what they are teaching. It was a very interesting book and I loved watching my daugther change as she read this book. She hates being told what to read so she started out with a chip on her shoulder. Then she slowly got into the book. Then she really got hooked and on the way to school every morning and the way home it was all she could talk about. The ending is open to interpretation and in fact the author won't really say how it ends. She wants everyone to interpret it how they want. It really doesn't take long to read...I think it took me about 4-5 hours off and on to get through it.