The moist hide could just be a temporary solution until you either switch substrates or figure out another way to up your humidity. Like Slim said...its a MOIST hide, not a swamp hide
Obviously your home and climate must just be dry, I would say switching substrate is going to be your best bet.
Using tubs like mike said does hold humitdy better but might not be something nice to look at, im assuming you just have the one snake and hes a pet. You'd probably prefere to see him well, like in a tank.
Its really up to you but 40% is too low for comfort, something should be done.