h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Yes, for social history, the nearer you can get to the voices of the people of the time, the more authentic. (There's a Mass Observation Archive of the ordinary lives of people in Britain -http://www.massobs.org.uk/)
But, when it comes to political history, aren't contemporary sources like to be biased? For example, General de Gaulle saw the French resistance as a force of French men of military background. But a recent book I've been reading, 'Fighters in the Shadows' by Robert Gildea, shows the truth as much more complicated. Many of the resistance members weren't French. They included Spanish Communists and Polish Jews for example. And many of them were women; maybe not fighting but acting as couriers and hiding Jewish children.
But all this means that, if you wanted to write a decent historical novel, you'd need to do a lot of good quality research.

Oh, I'm with you - but you also have to be careful with reassessments. Check and double-check their statements.

Why? Beside sloppiness, there's fashion. If it's currently the fashion to see it a new way, you may find yourself with information that's just as biased as the contemporary view.

Okay, we do not now believe that Napoleon was the Antichrist mentioned in the Book of Revelation. But what other ideas have crept in since 1815? You know what I mean.