It takes six milk crates to transport all of my dead-tree gaming books, so I scanned my favorites and stored them as PDFs on a thumb drive. They're easier to carry around, and don't get all mildewy that way.
I keep the 1st Edition Dungeon Master's Guide near the front door for when Morons and Jehovah's Witlesses drop by. 
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The mere fact that science may not yet adequately explain an object, event, or experience does not mean the immediate explanation should automatically default to a conspiratorial, extraterrestrial, paranormal, or supernatural cause.