Oh noes!
After a discussion on the internet, someone challenged that paper ignites at 451 degrees Fahrenheit, as Bradbury alleges.
After placing a shred of paper in my oven which was set at 550 degrees Fahrenheit, it did not ignite or burn.
Maybe the thermostat on the stove is wrong, and maybe there's a deeper philosophical meaning to books not burning at that temperature, but I think the answer came up in the discussion, which is that the title of the book should be Celsius 451!