I wonder how long the intro is in comparison to the journal.

I supplied the link. Without counting, about 12 pages.

https://babel.hathitrust.org/cgi/pt?id=coo.31924066186572;view=2up;seq=218

The journal is a great insight into the Egyptian campaign at that time. There's lots concerning the treatment of prisoners by N that is very positive, not so nice by the soldiers. Great insight into the army reaction to N deserting them. Well worth reading by anyone interested in the Egyptian campaign.