I'm currently catching up on the old classics I find here:
http://manybooks.net/
http://www.munseys.com/site/home
https://www.mobileread.com/forums/forumdisplay.php?f=126
http://www.feedbooks.com/
http://www.gutenberg.org/catalog/
I use the libprs500 library to convert when necessary.
I haven't tried to buy a book so far. But since there is no shipping involved, I'm sure you can find a way to create an account and hope they accept your Canadian credit card.
Cheers,
Sébastien