If the file is not in the desired format, tools like Calibre can convert it to PDF, Kindle (AZW3/KFX), or other formats [1].
JDT GRRM most likely refers to a digital, fan-compiled, or personal epub collection ("epub" format) of works by George R.R. Martin (GRRM), often featuring "JDT" (potentially representing Juego de Tronos or similar, or initials of a compiler) as a naming convention, sometimes compiled to manage the massive nature of his works in a single file or thematic collection [1].
EPUB is the standard format for e-readers like Kobo, Nook, and Apple Books, making it highly portable.
These epubs typically contain A Song of Ice and Fire (ASOIAF) novels, novellas ( Tales of Dunk and Egg ), and sometimes auxiliary materials like maps, character lists, or interviews [1].