It is probably best to obey the letter of the law, which pretty much states that downloading an ebook without permission (i.e. creative commons license, purchasing it) is illegal. Anything else depends upon a judge's interpretation. That may get you off in the long run, but still leaves you prone to a lawsuit.

In the past, Canada has had rulings related to both music and print books. eBooks, I don't know. The rulings that I have heard about pretty much stated that it is okay for a person to make a copy as long as they don't distribute a copy. The rationale and limits I'm unaware of.

It is also worth considering that the law is going to change in the next couple of years.