I’ve been getting into reading more biographies, and for the most part, it’s been great, but there’s always a lingering thought in my head asking: how much of this is real? I remember large phases of my life, and I get that a biographer would interview people around them/take countless hours trying to remember the past, but how can you remember so many things in such great detail?
If it’s a living person, then it’s relatively easy to research. There’s more than likely a lot of different sorts of documentation out there, not to mention the wealth of living people that you can interview, including but not limited to the subject of the biography. It’s less a matter of remembering and more a matter of asking the right questions, and then working the answers together in a satisfactory way.
If it’s a dead person, especially a long dead person, it’s somewhat more difficult, and you have to rely on more written sources. It’s more like historical writing, in that case.