The Friends of the San Francisco Public Library will Today commence its annual gargantuan book sale/social experiment on how insane people can possibly get about buying discount tomes.

More than half a million books — that'd be five big-rig loads — are up for grabs at Fort Mason starting at 10 a.m. tomorrow at the aptly named Big Book Sale. Literary aficionados fly to San Francisco for this event; the behavior of shoppers has been compared to the game show Supermarket Sweep.