One published in 2015, two new ones this year. Plus last month’s addition to the list:
Douroux is a journalist at Libération, who, according to the jacket, “spent four years tracking down the brilliant hermit. He has scoured [épluché] the archives and flushed out its last secrets.” Fat chance! Still, his book is at 5851 on amazon.fr’s best seller list, the others somewhat lower.
None of these books has been translated into any language other than French, as far as I can tell, and the definitive biography — the one on which the definitive movie will be based — has yet to be written.