Yesterday, I finally got off my fat ass and cut some pieces of 2x4, and today I unmounted the bottom shelf from its brackets and attached the pieces of 2x4 so that it can rest on the floor. Then I got started moving the 6 shelves above it to distribute the ~3.5" of extra space amongst all the shelves so they can all hold books. I got through 6 out of 8 brackets on the bottom shelf, and the batteries gave out in the drill/driver, so I'm taking an LJ break.
This project has been hanging over me all these months; knowing that I'm blowing it off has contributed in a small way to my depression, but every time I looked at it it was such a daunting task that I couldn't get started.
This time, at least, I made sure that a tall book sitting on the bottom shelf (now on the floor) clears the newly positioned brackets for the next shelf up before finishing the whole project, because if I did the whole thing and it was still useless I would probaby set fire to the house or something. Only a few more hours (of actual working) and I'll actually be ahead of the game on bookshelves.