This is a variant of the Stackable Box Shelf for IKEA Skadis. The only difference is on the back, hooks are in different orientation so that shelf can be used in line to save a little bit of space. Please look photos for clarification.

I printed them in PLA nad PETG. Supports are needed only for hooks. 

I included the original file skadis_box_shelf-Shelf.stl.

New version is named Stackable Box Shelf Space saver.