A tip for those who purchase books in Amazon two Americas (Amazon.com) is always taking a look at Amazon Canada (Amazon.ca) before closing the application. The prices differ from one store to the other, in general the absolute values are close in both stores, for example, a book that costs 100 US dollars at Amazon.com usually costs 100 Canadian dollars on Amazon Canada. The advantage is that the Canadian dollar costs less than the US dollar, then when converting to real the difference may be worth.
Do not forget to check the shipping too, because it is more expensive in Canadian Amazon (10,99 per package + 6,99 per item versus 4,99 per package + 4,99 item by Amazon States Unidense), and then the difference can not be that good. In addition the Amazon.com's economic freight has the delivery period similar to the priority of Amazon.ca (2 a 4 weeks, costing 15,99 per package + 10,99 per item), the economic Amazon.ca is quite slow (2 a 3 months).
Summarizing, for cheaper books generally Amazon US is cheaper, but more expensive books, say, from 100 dollars to top, Amazon Canada usually a better option, even using the priority shipping. Remember that sometimes appear deals on a website or other that make them very different prices, and then the rule does not apply, so each case must be evaluated, but it never hurts to do this check before every purchase.