Book stores are bracing for lower sales if there is a war:

Publishers and book retailers are nervously calculating the effect of a war in Iraq, worrying about lost promotional time and lost revenue. Book publishing is almost entirely dependent on the free publicity that authors receive in newspapers and on television and radio. On important programs, the time devoted to entertainment features will shrink considerably if a war occurs.

The most sophisticated retailers are the ones that are best able to anticipate "events" like war, bad weather (or even having the sidewalk in front of your store repaired); change their strategy in time to cope with the event; and, perhaps most importantly, be able to "remember" (i.e. record) what the impact of a give event is on its sales and which strategies did or did not work.