I built this in about an hour and a half with $20 worth of 6" pine lumber. It fits the space nicely, and got a lot of my books up off of the floor. I cut rabbet joints in the uprights with a router and a 3/4" slot bit, and nailed each joint with two eight-penny finishing nails. It’s easy to forget how strong basic joints are if you spend a lot of time doing fancy joints. The shelf is solid as a rock, and for 90 minutes, you can’t beat the functionality.
Note that the best way to cut rabbets for uprights like this is to clamp the two uprights side-by side, with their front edges clamped together… all the slots are then perfectly aligned, and with the two front edges clamped, breakout is minimized.
