Hi artemisblossom and welcome to MobileRead!
There are so many different formats it gets very confusing!
The 505 can read
epub (Waterstones and Fictionwise),
LRF/LRX (Sony's ebook store, also known as BBeB),
Adobe PDF (also called ADE or Adobe Digital Editions).
My preference is to buy books in epub if available. I would go for LRF second and Adobe PDF (ADE) third. For novels the PDF is okay. You will find that ebook libraries generally offer only the PDFs. And yes novels are offered in PDF.
I love my 505 and can't imagine reading books without it. There are a number of Canadian members around here and you should find some useful advice about ebook devices in Canada.
Check the wiki for more information on formats:
https://wiki.mobileread.com/wiki/PRS5...ported_Formats