But actually quite a few biographies and memoirs have been either partly or totally fabricated. Wikipedia lists 12 such examples since 2001, some of them completely fake. Like Michael Gambino's The Honored Society, in which he claimed to be the grandson of a notorious Mafioso. He was exposed by Carlo Gambino's real son, Thomas Gambino.
I've read a lot of autobiographies, including those by Michelle Obama and Keith Richards, and I've assumed that everything they say is true, but that's not necessarily the case.
Even if they seem more or less truthful, there are always things that by their very nature must arouse suspicion. Like long verbatim conversations. Whoever remembers conversations in such detail? For that matter, whoever remembers the entirety of their life in such detail? Isn't some of it what they think happened or would like to have happened rather than what really occurred? And might a few things have been tweaked a little to look more flattering, or less shameful?
Family members and friends often dispute what someone says in a biography or autobiography. They claim there was no such family feud, or estrangement, or disinheritance, or child abuse. Of course they would, wouldn't they? They don't want their good reputation dragged through the mud.
People who fabricate whole memoirs are so likely to be exposed by someone who knows the truth, you have to wonder why they do it. I suppose they calculate that by the time they're exposed they'll already have made a tidy sum from their sensational lies so it hardly matters.
