To an extent, all written history has a degree of bias. A book on U.S. history written by a nationalist is going to probably have greater bias than one written by a Swede specialised in humanitarian aid. Bias can't fully be avoided. This is why it's important to know who the author is, and be aware of any message that they might be trying to push.

Essentially, be a critical reader, and when you can, find multiple sources.