There are many differences, but the aside from usage the main difference is that current edition covers guidelines for electronic publications. The preface to

There are many differences, but the aside from usage the main difference is that current edition covers guidelines for electronic publications. The preface to the current edition is available online: http://www.chicagomanualofstyle.org/16/isbn_0226104036_pref.html http://www.chicagomanualofstyle.org/16/isbn_0226104036_pref....