I guess it's pretty clear from the text (and also from the ref mentioned below) that the narrative is in written form because it will be used for *reflective thinking*. It's possible to have oral accounts to do the thinking, but surely it'll be pretty hard, wont it?

Content of the notes are mentioned in the text (questions asked, usage of intentional talk, etc.).

Now, to get and idea of "narrative style", let me give an example (may not be a good one; I dont have exemplary teaching experience):

reporting style:
Class agenda: maths 9-9.40 am, english 10-10.40 am; three kids were absent

narrative style:
Today's class had two subjects (math and english). Of the twenty kids, Jim, Sarah, and Clark were absent, all because of influenza. The class started at 8.57 am with me asking "Have you done your homework, kids?" ....

Basically, the narrative style will try to grab any info that seems relevant. E.g. info on Jim's absence could be useful if he is the boy who's popular in throwing jokes (= affect the class mood).

Ref:
http://www.uwm.edu/Dept/IRE/research/Spring_2005.htm
Data Collection
In order to enhance the validity of the findings... Secondary data sources in the form of the prospective teachers’ narrative accounts of critical moments in teaching ...