they are motion activated, so when someone is standing there looking at books or walking by it sets them off. the beast within the books prop on the right pops open up to show the little monster with eyes that light up. it shakes and and makes some spooky sounds. with the possessed books prop on the left one of the books slides out back and forth and makes some spooky sounds. after using these two items for two years i have a few things to say about them. first off they work great. they don’t go off every time which is actually nice. you can’t depend on it to 