For books listed as Ebook the file structure is a bit different.
Those comics are listed as /view and contain the full image set. Other book types are not accessible in this way, forcing the user onto the PC / Mobile app.
You can query a PREVIEW of any book by its ID here. Free books returns the first 100 pages. Paid books return the first 20 pages (or less)
https://ridibooks.com/books/589000416/preview/generate
https://ridibooks.com/books/896000472/preview/generate
If you open those URLs you will find info like this
If you open one of the spine links you see text like this
Using this method I intend to add OCR of comics and preview imports to the Rooster Importer