Pulitzer Prize Winner

At 771 pages, I'm not sure what I was expecting, but I was hoping that this book would hold my interest.  I finished it in a day and a half, so I wasn't disappointed, but I will say that the last third dragged on for me.  I have mixed feelings about whether I feel this book was worthy of the Pulitzer Prize (I realize, of course, that I am nowhere near a qualified expert).  I wanted so badly to know others' opinions that I asked around, and when I could not find someone else who had read it, I took to Google to look for a review.  This is the first one I stumbled upon, and it neither destroyed nor confirmed my stance:

(Click to read review)  It's Tartt - But is it Art?  

At the beginning, I very much cared for Theo Decker as a character, but as the story hit it's climax, I was annoyed with his inability to grow up and listen to his conscience.  I felt at the end he failed to redeem himself.  Maybe this is what makes it an exceptional piece of literature - that people are talking about whether or not it is good enough. Maybe I was let down because it didn't have a happy ending, although I have read plenty of books without one that were gems.  This book has me stumped.  I don't know if I liked it, I don't know if it was worthy of the Pulitzer, but I know I want to talk about it.  Perhaps that is the point.