Reddit mentions of Innovera Universal Economy Bookends, Nonskid, 4 3/4 x 5 1/4 x 5 Inches, Heavy Gauge Steel, Black 54055 (pack 2)

useful things

I got a dual pair of bookends for ~$1.50. Nothing special about them, but they look nice.

Completely acceptable HDMI cord, $1.09. I bought two. Works fine, don't need to spend a fortune on a working HDMI

Small stretch of paracord, 10 ft, for $4.49. Got mine for camping

USB extender cord, 6 ft, usually used for extending a printer cable, $1.69

useless shit

Small tea bag holder thing that looks like a swan... I paid like a dollar and addressed it to a buddy just to screw with him

A big, red vuvuzela. I bought third-party for like two bucks

Pink lips car decal

Edit: eh, screw formatting

You need to get the bookends with tabs facing both ways. You put your (vertically standing up as normal) on top of the longer inner tab; your heaviest (not necessarily tallest) ones the closest to the vertical edge of the bookend. Make sure to use both bookends, or to push all the books up against a wall/shelf with the bookend. The heavy weight of the books will actually make the bookends very stable. If the bookend skids (unlikely, but you may have slippery shelves), you can use a few books horizontally on top of the outer tab (you likely only need one), or prop a book up diagonally like a doorstop (I do not recommend diagonally however because it will damage your books).

Experience: used to work at the college library shelving many many many heavy and/or tall books. I actually loved shelving the big-ass heavy books because with proper use of bookends they stayed goddamn still.