What Makes a Book YA?

It's time for the lastest installment in my never ending quest to understand what factors drive a book to be marketed as YA (young adult) fiction.

I've argued before that it's the age of the protagonist and nothing else, but people pointed out to me that some YA books have non-teen protagonists. So I was back to square one.

Then, this year at the LA Times Festival of Books this subject came up several times and many YA authors said that YA books need to have hope or an element of redemption. That I could buy into and it even help explained why I love YA so much...I adore hope! I love stories of redemption!

This year two of my favorite YA series have come to an end. These are both post-apocalyptic series with many bleak dark moments--The Last Survivors and The Hunger Games.

While the reactions to Mockingjay (the final Hunger Games book) have been varied, many people have felt that it no longer qualifies as YA. I disagree (since YA is a made-up marketing category) because I felt the book had hope. But it does lead to an interesting question...does hope look different to different people?

The Road is a book in which I've heard people say it's all darkness with no hope and others say it has hope. I haven't read the book, but I would come down on the side of hope from the movie.

What makes a book classified as YA in your opinion? And what does hope look like to you? Do you need a happy ending? Do all wrongs need to be made right?