I would recommend choosing another design. We have the nicely carved and painted Safari version that looks adorable, but functionality of a sling books case is terrible.
Tall books, like so many toddler picture books are, tip forward because the fabric provides no base stability. You can only really fit a few books total before it becomes a hazard to the books themselves... too many and the tot tryiing to put a book away all by himself/herself will be crushing pages trying to slide it in. Too few books and they all tip over.
Can you tell my nice bookcase dreams were crushed and I now loathe sling bookcases?
There is an awesome DIY bookshelf over in Simplifying / organizing, I'll try to run a search for ya.,
eta: this is the one we have that I now loathe http://www.amazon.com/GuideCraft-g83.../dp/B000FICDE8