I took a peek at your ideabooks. If you are looking for inexpensive shelves for a child’s room, that can be reconfigured as the child grows and needs change, you might want to consider the wall bracket kits and pre-finished shelves from the big box store. The 12” wide shelves can accommodate a wide range of toys and books.

Twelve to 15 inches.......depending what you have in books

11-12 inch