No, history books should not be destroyed. However I wouldn't mind if people were more familiar with how academic study of history works.
In anthropology (history, archaeology, etc) a major part of education is teaching the students to determine whether a source is trustworthy or not. This is pretty much what all research is based on and there are entire books written about source criticism for various areas of study. Part of learning this is also the acceptance that however objective we try to be, we're only human and always looking at things through our own cultural and personal filter. This doesn't mean people don't try their best, but they also learn not to accept their interpretation as the absolute and unchanging truth. Laypeople easily forget this, which then leads to some having a wrong image of what academic research is all about.
As for history books, I obviously can't summarize the vast quantities of writings about why the facts you read are trustworthy, but I'll take up a couple of things that are worth mentioning. The first is peer review. One thing peer review does is ensures that publications have valid sources, i.e. what previous writings or original research the writer has been using. Scientific tests are expected to pass peer review in order to be deemed as trusted.
Another I like to bring up are the original sources (archaeological finds, ancient texts, etc) are used in scientific research. I'm fairly familiar with archaeological methods, which is why I'll use it as an example. The methods are somewhat different when we're talking about written texts. In archaeology, the archaeologist is expected to document their findings in a way that can be identically replicated by anyone. Since archaeological sites can be studied only once before the original order of the finds is destroyed, there are rigid rules for documenting everything, including the earth type next to the items, the depth the item was found in, and so on. This way anyone can go through the whole process and make their own interpretations depending on the finds. And trust me, there are lots of interpretations that will be presented as solid facts in main stream media. The point is that that's okay, because as any scientific field, archaeology goes forward all the time and we gain new information that changes our perception of the past.
As for your question on whether we know a document is 100% factual, the answer is: it varies. I've already mentioned source criticism, which includes being aware of the prejudices at the time of the writing of the text. Surprisingly few texts were even written to be taken as true in the sense we now think of the term. People took liberties, often for political purposes, sometimes as an artistic measure and at other times they were simply quoting someone else who had their facts wrong for whatever reason. Because texts were copied by hand they also inevitably changed over the years. Sometimes sources were started to be copied even before they were finished. Nowadays researchers have ways of tracking down these changes in order to get a fairly reliable approximation of older manuscripts. This yet again doesn't mean our current understanding of something is 100% reliable, only that we're getting better and better at getting there.
As a matter of fact, even videos or similar documentation will never be able to convey the full, objective truth of the past. There are always parts of the puzzle missing and new interpretations coming in. There are no absolute truths even in the now. There is always speculation going on on the news, theories of what someone was thinking. The pieces of truth are spread all over humanity and all you'll ever see anywhere is simply the approximation.
