Certainly looks like a desktop/laptop only application. Rather like the other desktop computer applications like Mobipocket, Stanza and such - without the handheld device support.
Also looks somewhat closed - you'll have to buy from Blio's shop.
... but there's this:
"• Can I download free Google, Gutenburg and Feedbooks with Blio?
Yes. To download free, public domain books from Google, Gutenburg, and FeedBooks, just go to the file menu and click on the website you would like to download from. These websites provide over one million fiction, non-fiction, reference, textbooks, children’s books, scientific, medical, professional and educational books at no cost."
I wonder if that means you can add your own files (in recognised formats, whatever they are) - or just add books from certain sites that are somehow integrated with Blio.