Doug Nufer's Never Again, a novel of approximately 40 thousand words, is by far the longest text in which no word is repeated. In the Feb 1995 Word Ways I published a two-hundred-word essay on this topic, using each word only once, and noted that H.J. Verschuyl had created a document of similar length in Dutch, reprinted in Battus's Opperlandse taal- & letterkunde (Querido, 1981). The longest-known accidental text is a 66-word window from Rudyard Kipling's "Brother Square-Toes" in Rewards and Fairies, reported by Mike Keith in the Nov 2002 Word Ways.
Eckler, A. Ross
"Text With Each Word Used Just Once,"
Word Ways: Vol. 36
, Article 22.
Available at: https://digitalcommons.butler.edu/wordways/vol36/iss3/22