Timeline for notification of teaching duties for Grad TA
Most likely something fell through at the last minute and they had to find coverage. It could have been handled better (i.e. asking rather than just telling, explaining the situation), but it does happen that a class might suddenly need to be reassigned much closer to the start of the semester than normal. 

(Adjunct professors often get last-minute teaching assignments, and last-minute cancellations.)

You can certainly ask them if they can reimburse you for the cost of the textbook shipped to you at home. I've had my department reimburse me for expensive overnight shipping for stuff I needed for prep when they assigned a class to me at the last minute (a week or two before classes started, in a subject I barely knew. That was fun.) You can also ask if, given the late notice, they can help you out with materials and lesson plans from the last person who taught it.