Remember, you are working on a 1.9.19 which supported only for security fixes ... not other fixes (like book add-on). Take it you did download the most up-to-date version of book for 1.9.x.
Don't re-call there being any settings like that for book in 1.9. Having said that, however, there might be ... then again, might be the theme.
Am not sure that the book in version 2 of Moodle (where you will eventually end up) has the same issue or not and if this will auto-correct or not when finally arriving at destination.
The only thing I could suggest is looking over the code for book on the server to see if there is anything that could be corrected or since you already extracted the backup zip and saw references for the contents of the 'books' in the course, was there any HTML in there?
Maybe a 'book' expert could contribute here at this point.
Think I saw someone who posted in these forums a 'rule of thumb' for working with Moodle ... always keep it up to date. Makes sense to me. These 'little issues' can get fixed earlier and one stands a better chance of things working rather than waiting (skipping versions, etc.) for the problems to compound themselves.
Will you have to go into each and change justification? Maybe! :|
'spirit of sharing', Ken