Short answers, pulled from the story.
Emmanuel de Las Cases, born the 21st of June 1766 and died the 15th of May 1842, was a French nobleman, cartographer, and writer best known for Le Mémorial de Sainte-Hélène. He compiled this record of conversations with Napoleon Bonaparte during Napoleon's island exile on Saint Helena, then published it in Paris to wide acclaim.
Le Mémorial de Sainte-Hélène is a book Las Cases compiled from notes he took while serving as Napoleon Bonaparte's informal secretary on the island of Saint Helena from 1815. He published it after returning to Paris and made a fortune from its sales.
Scholars consider the Mémorial unreliable in parts. Las Cases inserted his own thoughts, colored Napoleon's expressions, misstated facts, and in some cases fabricated documents outright. Pages corrected in Napoleon's own hand survive at the Wisbech and Fenland Museum in Wisbech, England, as physical evidence of the discrepancies.
Las Cases published the Atlas historique, genealogique, chronologique et geographique under the pseudonym A. Lesage in London in 1801; the first French edition appeared in 1803-1804. Multiple editions and translations followed, several pirated, and the atlas continued to circulate into the 1850s. It made Las Cases wealthy.
Las Cases was expelled from Saint Helena in November 1816 by the British governor, Sir Hudson Lowe, for infringing British regulations. He was sent first to the Cape of Good Hope, then to Europe, where the government of Louis XVIII initially refused to let him enter France.
Las Cases died on the 15th of May 1842 in Passy, at the age of 75. He is buried in Passy Cemetery.