How true should a book be?

It should be 99% true. If a line is bent, it’s not a line anymore; if the truth is bent, it’s not the truth anymore. To be a non-fiction book, almost everything said should be able to be backed up by factual evidence. Authors should be given a little wiggle room though. They could take out small details that are boring and just hold the story back. If you’re writing a story about Neil Armstrong landing on the moon, you don’t want to add a bunch of irrelevant astrophysical equations; no one wants to read about that. Also, the dialogue isn’t going to be 100% true; no one knows or remembers the exact words said between Houston Control and the astronauts on the shuttle. The author of a non-fiction novel can leave things out and reword things that happened, but they shouldn’t be adding any fictional events or characters to the story. It’s important to keep the story going but it’s more important to keep your non-fiction novel, non-fiction.