This is the result of a couple of the ideas floating in my head. One make a bookshelf with a self closing bookend, two make things that use the advantages of different materials. 3D prints are very flexible in the shapes that they make and are fairly strong. But why use it on everything. I wouldn't trust filament on filament rubbing together not to wear. It would probably wear books rubbing on it. Getting some supplies from the hardware store may cost a little more than an equivalently strong amount of filament. But it saves a bunch of time and is more durable.

This is meant to be used with paperback novels or DVDs. I styled it to look like laser cut steel with some bits welded and bolted on.

Supplies from hardware store:
2 - 1/4 x5in bolt (attaching left and right side with coupling nut)
2 - 1/4 x4in bolt (attaching bin to side/ moving bookend)
6 - 1/4 in hex nut
optional 2 - 1/4 in washers
1 - 3/16in x 3 ft metal rod to be cut into 3 - 10 in pieces and 4 - 3/4 in pieces
1 - coupling nut
finishing nails if you don't have any
something to add weight to the hanging bin

To assemble it first cut 3/16in rod into three 10 in pieces that will go between left side and right side. I wasn't able to cut with pliers and had to use bolt cutters. Put together left side, right side, three 10 in rods and two 5 in bolts. Put a nut on each 5 in bolt and the coupling nut halfway on each 5 in bolt, then tighten nuts down on coupling nut for loosening prevention.
Use some pieces of 3/16 in rod to assemble rod end onto hanging bin/ rod end hanger and book end. The pictures and prints should give the gist of how it goes together (two half rod ends in four places). Some gluing may be necessary depending on how permanent you want it to be.
Use the couplers, 4 in bolts and four remaining nuts to attach it all together (two nuts on the end of each bolt and tightened together onto the coupler).

I used some cheap white PLA for the prototype in the picture. Then I tweaked a few things to make it work better. Most noticeably the hanging bin is larger and I've specified using shorter bolts on the hanging bin. I think this PLA would look better:
US-

Canada-