A visitor to Lisbon will meet with the name of this philanthropist of Armenian origin all the time: Calouste Gulbenkian (1869-1955; Wikipedia). The foundation that bears his name is preparing an official biography edited by Jonathan Conlin and to be published for Gulbenkian’s 150th anniversary. Last fall, José Rodrigues dos Santos, a best-selling author and TV anchor (homepage, Wikipedia), presented his fictional biography in two volumes, for which he claims to have visited the places where Gulbenkian lived, but for which he did not consult the sources available at the foundation, according to a spokesperson there.
The first volume is called O Homem de Constantinopla [The Man from Constantinople; review excerpts from the author’s homepage], the second Um Milionário em Lisboa [A Millionaire in Lisbon].
Two of Rodrigues dos Santos’ previous novels are available in English, The Einstein Enigma and Codex 632: The Secret of Christopher Columbus. Judging from his sales, he knows how to entertain a broad public with thick books.
As to other non-fictional biographers, already in 1957 Ralph Hewins presented Mr. Five Per Cent, for which he consulted some sources and talked to family members.