These are usually created for offline reading, easier navigation, or consolidating the series ( Game of Thrones book series) into a single digital volume rather than separate files [1]. How to Find and Use These Files:
EPUB is the standard format for e-readers like Kobo, Nook, and Apple Books, making it highly portable. JDT GRRM epub
Are you looking to download this, or are you trying to create one yourself? These are usually created for offline reading, easier
They can be read on apps like Books (iOS), Google Play Books, or Calibre on desktop [1]. and Apple Books
If the file is not in the desired format, tools like Calibre can convert it to PDF, Kindle (AZW3/KFX), or other formats [1].