It's paper - and also (almost) glueless. Brian Bartlow of Lone Tree Games is an engineer by day, and did all the construction of these sets. I do the textures. It's just a matter of folding and tucking in the tabs. If you're really keen you can get a robo-cutter and it does all the cutting for you, as Brian created the files to work with them. It's pretty amazing.

Just got a 5* review for this on RPGNow and Paizo that said that it's so easy kids could make it - so I'm saying it's not crazy to give it a go. If all else fails, you can just print out another wall to replace the one that got stood on/torn/eaten.

Edit - Thanks RobA, I've sent a quick correction to the guys at Paizo. Much appreciated.