The variables were set upon creating the books in the locations you found them.
Do you have 6 books in total? There also exists a book "SUFBOOKA" that doesn't seem to be created via script, did she have it already? EDIT: Yes, you wrote it above. So, I guess Nashkell Carnival is the best available area to try it.
Areas with the appropriate script blocks are: AR1900 (BanditCamp), AR1803 (CloakwoodMines_L4), AR2400 (Peldvale), AR2600 (Candlekeep, Prologue), AR4002 (Gullykin_JenkalsHouse_Cellar), AR4900 (NashkelCarnival).
Of course, for Tutu it's not "ARXXXX" but "FWXXXX" in case you want to cheat your party there.
If you first enter one of the areas with all 6 books, there is a timer of 30 seconds before they are combined, so don't be unpatient. Hope it will work now!