The Dune Encyclopedia: The Complete, Authorized Guide and Companion to Frank Herbert's Masterpiece of the Imagination

The Dune Encyclopedia is an expansion of the Dune universe, background and commentary in the form of a reference text compiled and edited by Dr. Willis E. McNelly in 1984. A total of 43 people contributed articles to the work.
The book was based on the first 4 books of the original Dune saga by Frank Herbert, namely Dune, Dune Messiah, Children of Dune, and God Emperor of Dune. At the time it was written, The Dune Encyclopedia was promoted as the "official" Dune chronology. Frank Herbert, who was a personal friend of Dr. McNelly, wrote the foreword for the Encyclopedia. Rumors existed that Herbert himself contributed to it; however, if this were true, he wrote under a pseudonym, as his name only appears on the foreword.
Despite the Encyclopedia being hailed as an official reference text for the Dune universe, some of the information contained therein was contradicted by Heretics of Dune and Chapterhouse: Dune.
The Encyclopedia also presents itself as an in-universe document. It was published in 15540 AG, and its editor was Hadi Benotto.
The Encyclopedia provides a timeline both based on the Dune chronology by Frank Herbert, original dates of original, never-before-revealed in-universe events, as well as real history, seen from the Dunish perspective of the Imperium; the history of Terra is seen as the history of an "Imperial Seat," started by Alexander the Great and carried over by Rome, Madrid, and London, until the "interprovincial war" of World War II, when it is transferred to Washington, D.C. for the next several centuries.