The Liber Linteus Zagrabiensis ( or Liber Agramensis ) ( Latin : Linen Book of Zagreb or Book of Agram ) is the longest Etruscan text and the only existing linen book . The Liber Linteus Zagrabiensis ( also rarely known as Liber Agramensis ) ( Latin for Linen Book of Zagreb or Book of Agram ) is the longest Etruscan text and the only extant linen book .