Both your points are correct. The account is the same as you would set up if you purchased an ebook on their site. Once purchased, the ebook is made available in your account for download. You can also read the book online from the account in some sort of browser-based reader, but as far as I know all of their ebooks are available for DRM-free download in PDF and other formats (such as ePub - I'm not sure if all formats are available for all books).
And yes - you have to visit the site each day to find out what the book is. I believe the new book is made available (and the previous one unavailable) at 4:00 PM Pacific time. Kind of a drag, but oh well.