There's so much history that isn't taught in school (politically covered up) and Zinn presents many of these little-known history gems. Be warned, there is a light liberal swing.
http://hnn.us/articles/1493.html:
“Objectivity is impossible,” Zinn once remarked, “and it is also undesirable. That is, if it were possible it would be undesirable, because if you have any kind of a social aim, if you think history should serve society in some way; should serve the progress of the human race; should serve justice in some way, then it requires that you make your selection on the basis of what you think will advance causes of humanity.”
Also I agree that you can't be objective in history, all sources have their bias.
I'll put smileys next to jokes next time, OK?