Here in the US I believe Best Buy's return period is now 14 days, likely the same in Canada. Here is
Chapters' return policy, which says 30 days for "most items". Again, I'd give them a call and ask if ereaders are an exception to that 30 days so you know what to expect.
Although I'll add that it's normal for all stores to no longer give refunds even for defective items after the store's return time period. At that point you always need to deal with the manufacturer.