Lots of book shelves.
Our daughter literally had 1000's of books.
She would rather have any toys or anything else.
We filled her walls with shelves.
She learned to always put her books back on the shelf. In the beginning they were stacked in piles, but on the shelves.. then as she got older, I "allowed her" to organize them.
She was good about putting all of the "Little Critter" books together
All of the "Robert Munsch" Books together.
The Nursery rhymes.. etc..
Fairy Tales
Eventually she got taller and so the picture books were on the lower shelves and the chapter books began to be on the higher shelves.
We packed up the baby books.. I then donated them.
Then when she came across books she really did not care for I packed them and either donated them or sold them in garage sales.
Eventually once she was in elementary school, we had a huge clean out. Again donated or sold the "do not want to keep forever books", The rest were boxed and placed in storage.
Once she was getting ready to leave for college, we once again reviewed all of the books with the reminder... "These books will be yours the first time you move into your own place. We will not store them until you may or may not have children. " And so we have many, many boxes of her books and each summer, she goes through them and weeds out more and more.
This Christmas I actually made our "Tree" out a very small portion of her childhood books. I added a big silver star to the top and wrapped a strand of lights around them!
She was pretty excited to see some of those books, there are others she said, she "needs to weed out".. hee, hee,.