This must be in a place with a seriously dry climate. No outdoor books in a rainy land!
Where on Earth would it be dry enough to hang a bed from the trees and not have a nasty mold problem to contend with? Here in Seattle this idea just makes me laugh and laugh and laugh. It will be sunny for an hour and then a sudden downpour soaking everything for fifteen minutes. By the time you get the damned thing off the platform and under cover, the rain will stop and the sun will come back out. Ridiculous.