Not much is known about the appearance of each book, but the book containing The Ten Tails is shown as a slightly tatty volume with various rips and tears in the cover. It has Zeref's name written in large black letters on the cover and the spine. On the front cover, there is a picture of a glowing eye in darkness with several wavy lines spiraling inwards towards it.
The books contain knowledge on the Black Arts which Zeref used. Many of the spells known to come from the books involve the summon of Tailed Beasts. Each Tailed Beast is summoned by their own book.