We love picture books at our house. We purchase them for our children on each birthday, holiday, etc. A few years ago, we reached the point where there were too many books and no organization. While shopping one day, I came across a clearance sweater organizer, and realized that it would be the perfect solution for our book problem. It has worked out really well.
It holds a LOT of books. It's hidden away in the closet. It doesn't take up much space. Inexpensive! Accessible for the kids!
Hopefully this idea can help you get more organized too!