Why would an informative history text book source be unreliable?
A secondary source, such as a text book, will never be as reliable as a primary source. Historians will always be influenced by their political, religious, economic and social views, and by the times in which they live, and we cannot help unconsciously putting these onto our work when drawing conclusions and explaining facts and events. This is why secondary sources are never free from bias, and as such can be judged unreliable. When someone writes a textbook, they may omit information they do not think is important, as you can not possible include every piece of information in a book or journal or whatever, meaning you get only a partial view of the event. Also, a history text book may be relying on the conclusions of other historians, without making any effort to evaluate their bias or influences.
