libraries with movable stacks make me chilly. you know very well you can't be crushed to death in them, even in the days of hand-cranked shelves you can at most hide a dead body between them - but i am sure that they prod at some deep-seated psychological fear in you - associated with the dangers of crossing a mountain pass - bandits, or ambush by the enemy, landslides ("miss flitworth, the mountains can be very dangerous at this time of year,") into the valley of death rode the noble six hundred. the feeling of treachery and danger - being forced into and along a single trajectory, narrow passage, the sheer walls rising on either side. and this feeling of sinister crossing is created right at the start - for there is something magical and precarious about it - as the stacks begin to move open silently - the parting of the waves, perhaps, or a opening of a magical door, a crack in a stony ediface - the first narrow slit of darkness, and then a light at the other end as the shelves widen more, and then a eerie stillness.