Originally Posted by PeterT
The Kobo Desktop app only reads Kobo format material; ie the books IT downloaded from the Kobo Bookstore; it will NOT read ePubs.
For reading ePubs on your Mac desktop, you can try the Sony Reader app. https://ebookstore.sony.com/download/
I enjoy that interface when reading at my computer.
Also, Adobe Digital Editions. It's not as pretty, but it's very fuctional for reading.
Finally, Calibre itself will let you read books. Very basic functionality, as I don't think you can highlight or make notes. But it's very nice and simple as a text reader.