I believe or assume that Volapük, Esperanto, Ido, Interlingua, Interlingue, and Klingon each have at least a few translations of important literature such as the Bible or Hamlet. What other constructed languages have been used for extended writing, either original or translated, as opposed to sample texts and the like?
To put it another way (which is not quite synonymous but close enough), what is the longest single composition in – for example – Bolak, Solresol, Toki Pona?