The phrase "original novel" refers to a book that is completely new and unique. It is not based on any other story or previously published work. Full definition
It is an ingenious, wholly original novel — a literary tour de force that is a triumph of art and spirit. (bookbrowse.com)
Overall, this is one of the more original novels I've read this year. (goodreads.com)
The game within the game this time is Gun Gale Online, filled with characters you'll know from original novels, previous games and the anime series. (thesixthaxis.com)